Energy Efficiency Intervention Program in Steel Re-rolling mills of Gujarat, India

Transcription

1 Energy Efficiency Intervention Program in Steel Re-rolling mills of Gujarat, India Supported by Implemented by International Centre for Environmental Technology Transfer, Japan Winrock International India

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3 Energy Efficiency Intervention Program in Steel Re-rolling mills in Gujarat, India Supported by Implemented by International Centre for Environmental Technology Transfer, Japan Winrock International India

4 Acknowledgements This document comprises the outcome of the Energy Efficiency Intervention Program in Steel Re-Rolling mills in Gujarat supported by International Centre for Environmental Technology Transfer (ICETT). Winrock International India (WII) would like to acknowledge the support of ICETT. WII would also like to acknowledge the following agencies for their time and unrelenting efforts in making this intervention a success: q International Centre for Environmental Technology Transfer (ICETT), Japan q Bhavnagar Steel Re-Rollers Association, Bhavnagar, Gujarat q Sihor Steel Re-Rolling Mills Association, Sihor, Gujarat q Allied Furnaces Pvt Ltd, Mumbai, Maharashtra q Ace Consultancy, Bhavnagar, Gujarat q Shree Ramdev Steel Industries, Sihor, Gujarat q Vijay Steels, Sihor, Gujarat q Raj Steels, Vartej, Gujarat q Hans Industries, Sihor, Gujarat q Triveni Iron & Steel Industries Pvt. Ltd., Bhavnagar, Gujarat q Garg Casteels Pvt. Ltd., Bhavnagar, Gujarat WII also acknowledges the efforts of the project team including Mr Manish Soni, Program Officer and Mr Chaman Kumar Shukla, Program Associate who worked relentlessly to ensure that the intervention was a success. Winrock International India (WII) Winrock International India S-212, 2 nd Floor, Panchsheel Park, New Delhi Tel: ; Fax: Website: The content appearing in this document may be quoted or reproduced without charge, provided the source is acknowledged. All images remain the sole property of their source and may not be used for any purpose without written permission of the source.

5 Contents Preface Messages v viii Chapter 1: Understanding the Clusters 18 Chapter 2: Methodology 23 Chapter 3: Implementation Plan 34 Chapter 4: Activities Undertaken 43 Chapter 5: Roadmap for Future 61 Chapter 6: Dissemination and Replication 63 Chapter 7: Results of the Intervention 65 Chapter 8: Capacity building of stakeholders 77 Messages 79 Chapter 9: Fundamental Technologies on Steel Rolling 85 Chapter 10: Fundamental Technologies on Reheating Furnace for Steel Rolling 101

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7 Preface I am very pleased to have this opportunity to write this note on the success story on improvising technologies for energy conservation and productivity enhancement in the rolling mill cluster of Bhavnagar, Gujarat. The basic intention behind preparation of this manual is record the success path and the challenges experienced during the implementation and share this with all relevant stakeholders in India. We strongly believe that this will really add value on the expertise and experience to the parties involved in such intervention anywhere in any sector in India or otherwise. It is extremely honored to have obtained the chance to contribute as one of the person leading this project Dissemination of Energy Efficiency Technology in the Rolling Mill cluster in Gujarat, India on behalf of ICETT, Japan, while this note goes for publication, I would like to take this opportunity to express my gratitude to all the people (who are many in this case and so could be named individually) because of their untiring support and effort to contribute to the cause of Sustainable Development and that s the very reason that its really gives good feelings when I take a look back recalling this very important project activities for the past four years. Well, you all must be aware that the economic growth of India of recent years is the one to be exactly amazed, and it remains in high level following China in the rising nation in the world. The economic growth rate in maintains about 7% after a worldwide economic crisis where the advanced country falls into negative growth across the board, and the growth of last year ratio +9.7% and +8.4% in 2011 is forecast in the prospect of IMF in The growth is thought to be present continuation though the inflation etc. are taken up as a matter of concern, and it is said that it will become a world economic power in the middle of the 21st century in a part of view. In other aspect, it is said that the environmental problems caused by the increase of the energy consumption in the industry according to economic growth will be more important than before. The import dependency of oil in India is 70~80% and expected to be 90% near 2030, according to IEA (International Energy Agency). It is not an exaggeration to raise the energy efficiency and to suppress the consumption even a little for the development of Indian economy as one of the high-priority issues. On the other hand, when eyes are turned to an environmental side, the Global warming is a big problem. It is not a problem of one country, but there is a problem of common but differentiated responsibility for the countries all over the world across borders in global warming. The greenhouse emission burden of India is about 1.4 billion tons (about 5% of the entire world in 2008), the world s fifth emission in the world after China, United States, European Union (EU), and Russia. However, the amount of the emission per person has greatly fallen below about 1.3 tons and 4.4 tons of the global average. Under such situation, Indian government has announced the greenhouse emission burden per GDP as an independent target that considers the situation of the home country to v

8 reduce 20~25% by That is looking both sides of the above-mentioned energy securing and global warming. Energy conservation is ranked as one of the most effective solutions. It is not only just for this solution of the both sides, but also brings the profit by the cost reduction to the enterprise, and improves life of the employee who works there. That is, energy conservation may be called an effective measure that brings a lot of benefits to the world (global warming), to the Indian country (economic development maintenance by the energy securing) and to the enterprise management and workers life etc. International Center for Environmental Technology Transfer (ICETT) to which the author belongs is an organization of non-profit that was established with the donation from Mie prefecture and Yokkaichi city, and furthermore, the enterprises in the vicinity in It is established to transfer the Japanese environmental technology to countries mainly composed of Asia, and various activities are done in the subsidiary of Ministry of Economy, Trade and Industry (METI) in Japan. It undertakes business not only concerning air or water pollution caused by industry, but the business concerning global warming etc now. ICETT had conducted an investigation to reduce the greenhouse emission burden and to do the business cost reduction of the enterprise (increase of the profit), about active business situation of the conservation of energy activity and the investigation for narrowing the target state and industry with assistance of METI in fiscal year With the cooperation of Winrock International India (WII), the information of the region and industry to support business in the future including the potential of resource and energy conservation in India was investigated and the needs information in the locale were collected upon the investigation. As a result, it was looked that it was a stage where Conservation of Energy Law was enacted in 2001, and it was recommended by an independent approach as a policy in the country. Five ministries including ministry of power execute the management of the energy sector as a governmental organization, and furthermore at states level, the organization entrusted with the conservation of energy promotion etc. in most states. That has been understood as a system. On the other hand, there are a lot of enterprises that place a top priority on production expansion under the remarkable economic growth, while it seems that there is a little recognition concerning the importance of energy conservation. The rolling mill industry of Gujarat state was selected through the investigation for the reasons of following. 1) Potential of energy conservation. 2) The support of state and enterprise to the project. 3) The possibility of the dissemination of the result. In fiscal year 2008, Mr. Tezuka, a Japanese specialist was sent to the region to attempt the conservation of energy improvement of the heating furnace in the model enterprise, and the site investigation was done with WII and Allied Furnaces, engineering company in India. Finally, we narrow down the object enterprise to Vijay Steel, and also got the cooperation of Garg, Steebars Re Rollers, and Triveni Co. The improvement was made, and the schedule adjustment for an actual improvement was done. It was uneasy, fur from small risk such as the production stop losses for the improvement construction was got over by the bold decision of Mr. Muraliral Gupta, the owner of the Vijay Steel, and the improvement construction was vi

9 started on November 2, and completed on November 22 in Though the content of the improvement is omitted here, it thought to be described later. The effect of the improvement came to be remarkable, for the coal unit requirement to be improved by about 30%, and for the scale loss to be reduced from 8 to 5% by 3%. The result of the improvement was shared with the distinguished and learned people of Bhavnagar including Mr. Mehul Vaddaria, the president of Saurashtra chamber of commerce and industry, Ms. Vivhavariben Dave, the Gujarat state assembly member, and Mr. Rajubhai Ran, MP, Bhavnagar and all the concerned person related to the rolling mill industry, and it received a lot of praises and understanding for the Mr. Muraliral Gupta and this improvement activity at the workshop in February In next fiscal year 2010, to develop this project, the objective of this activity was expanded to other enterprises widely with adding another Japanese expert Mr. Hitomi. As the intervention concentrated in the three the Raj Steel, the Ramdev Steel, and the Sardar Steel, out of which the successful results are demonstrated in first two mills and third one is on the verge of doing the same. I feel for these four years that the manager and parties concerned to the enterprise in Bhavnagar district are very ardent to the technical guidance in this project. I was convinced that it was not wrong to select this district and industry after touching an enthusiastic question and demands about the technical guidance for their enterprises from the ardent attendee in the two times workshop. Moreover, it is felt a basic factor for this project to achieve the result that they are very friendly and kindly to us visitor from Japan. I hope this technology not only to stay in Bhavnagar district, but also go to places and get developed in other districts and states, and to bring a big and significant impact to the environment and energy reduction in the future. Finally, I would like to express gratitude to WII that acted from the investigative phase till this dissemination as a partner, and Allied Furnace for their technical cooperation, and the local coordinator from Ace Consultancy for the valuable advice and cooperation during the dissemination activity in the district. It is much obliged if this small chance contributes to friendly relations between India and Japan, and contribute to the global warming control in addition. Mr Yoichi Takaishi Director of Global Environmental Unit International Center for Environment and Technology Transfer vii

10 Dr Kinsuk Mitra, President, WII Message from The President, Winrock International India We are proud to acknowledge that the co-operation between ICETT and WII in motivating the Bhavnagar rolling mill industry cluster to adopt cleaner technological option has been a very successful intervention. There were many challenges for the team when they started their work but with due support from its partner Allied Furnaces, they could overcome whatever challenges that came in their way. Today, the success of their hard work is present for everyone to see. For others interested in similar work, this will serve as a learning platform as an ideal intervention model in MSME sector. The success achieved has the potential for wider up-scaling and we are keen to promote this in a big way so that entrepreneurs and other stakeholders can replicate and take this success story forward. To assist with this process, we found it important to document the success story and make it available in a user friendly manner. The DVD documentary and the dissemination material will go a long way in establishing the future linkages for expanding the horizon of this project and we at Winrock International India would definitely like to take this initiative to greater heights in future and contribute to the larger mission of sustainable development. Dr Kinsuk Mitra President Winrock International India viii

11 Message from the Vice President, Winrock International India The cooperation between ICETT and WII in motivating the Bhavnagar rolling mill industry cluster to adopt cleaner technological option can be viewed as a very successful intervention. The success achieved on the ground and the way the project team, with excellent support of its partner Allied Furnaces, overcame the many challenges that came up during the course of the project makes it an ideal intervention model in a MSME sector. Highlighted below are some of the salient features of the project that makes it unique, not just in terms of its achievement, but also the process followed. Somnath Bhattacharya Vice President, WII Approach of the project team: While Bhavnagar was an ideal cluster in terms of technical potential for energy saving and environment improvement, the team faced a very luke-warm response from the local industry initially as many other interventions in the past just ended up with a study report leading to the industry losing faith on such initiatives. So the first task for the team was to build trust and credibility for which the team followed a bottom up participatory approach engaging the local industry association and opinion leaders in the cluster in a very effective way. Quick transition from demonstration to replication phase: The results of the demonstration phase provided enough incentive for the local entrepreneurs to line up for implementing similar measure in their plants. The entrepreneurs not only paid the entire hardware cost, but also agreed to share the cost of engaging Allied Furnaces as technical backstopper/technology knowledge provider. It is not very common to transition from a demonstration phase to an up scaling phase, as it happened in Bhavnagar. Encouraging results on the ground: Results established so far in the replication phase has been very encouraging. The furnace efficiency has improved by 20 to 40% and the scale loss has reduced by 2-5%. It has already been 3-4 months since the commissioning of the new furnaces and they are running quite well on sustainable basis. ix

12 Wholehearted participation from the industry: It is very rare to get such cooperation in a MSME cluster. The environment has been made quite congenial with the kind of awareness that has been brought by the initiative and industries are now eager to participate in more numbers Possibilities beyond Bhavnagar: The way the dissemination material is prepared and ready for distribution this coming month, other cluster intervention is a real possibility even though the approach have to be customized as per the cluster dynamics which definitely can be taken care of. Apart from Jaipur, Raipur and Mandi Gobindgarh, there are lots of possibilities in the states of kerala, Karnataka and tamilnadu which can be explored in coming days. CDM development: The intervention so far has set a very good platform to generate emission reduction credits and can really give support to the project in future for extra financial incentive and should be pursued. Future road map: A mix of dissemination and replication in Bhavnagar as well as in other clusters would give help broad basing the project activities and CDM ability of the actions can also be explored in the upcoming phases of the project. Somnath Bhattacharya Vice President, WII x

13 To, The President Winrock International India New Delhi Subject: ICETT sponsored Energy efficient furnace design in Bhavnagar cluster to reduce global warming Dear Sir, We take this opportunity to express our gratitude to your firm and ICETT for giving us a chance to improve the efficiency of re-heating furnaces of our member units. The project started three years ago with extensive research and energy audit by experts of Winrock International India. The energy and pollution audit of the selected units had given some eye opening results. Our member M/s Vijay Steel accepted the offer for becoming a model unit. The results were positive and many units have shown interest in adopting this new technology. The technology dissemination workshops for mill owners and technical staff had helped tremendously in generating interest for the new technology. For the first time we started implementing our social responsibility and reducing greenhouse gases for the benefit of mill owners and people of surrounding area. We wish that the project will continue further as more mill owners are coming forward to adopt new technology and design. Also, your help in improving rolling technology and efficient use of electricity will make the cluster an ideal energy efficient cluster of India and we can move together for a clean, green and sustainable society. Thanking you Yours sincerely President Sihor Steel Rerolling Mills Association xi

14 To, The Project Coordinators M/s Winrock International India and M/s ICETT, Japan Subject: Energy efficient furnace design to reduce pollution in Bhavnagar area. Dear Sir, We express our hearty appreciation for the Project in Rolling Mills of Bhavnagar and Sihor. The selection of Bhavnagar cluster was done after extensive research. Primary studies by experts had shown that the furnace efficiency of traditional furnace was quite low and the pollution level was more than expected. With constant persuasion by the local coordinator, Winrock International India team and visiting ICETT officials, a motivating atmosphere to encourage the thought process towards efficiency and capacity building was started. The members were enthusiastic about the proposed changes, however, the main constraint was the budget and the time required for modification. Any support from financial institution would help in faster implementation of the project. We hope that the project will be sustained with further technical assistance from your organization and the activities will spread to other areas of mill activities like rolling technology, electric consumption and maintenance. We extend our heartfelt gratitude and thank you for your efforts and commitment towards a clean and green environment. Yours sincerely, Bhavnagar Rerolling Mills Association xii

15 Note from the Project Coordinator The conceptualization of any energy efficiency intervention is mostly guided by the cluster dynamics. Bhavanagar Re-rolling cluster has its unique characteristics due to its very linkage on the raw material supply from Alang Ship Breaking Yard. Whereas Alang Ship Breaking Yard has been a constant source for sustainable supply of scrap based ship material, the cluster has shown its strength among many adversities from big steel producers to market dynamics. Debajit Das Program Manager, Climate Change/Environment WII ICETT s belief that this is a prospective cluster for implementing this initiative was the core for starting this project. Unknown to the cluster characteristics, our first job was to understand the people who run the industries both at operational and management level, the process and its linkages to the energy utility. The cooperation between ICETT and WII in motivating the Bhavnagar re-rolling mill industry cluster to adopt cleaner technological option can be viewed as a very successful intervention. The success achieved on the ground and the way the project team, with excellent support of its partner, Allied Furnaces, overcame many challenges that came up during the course of the project makes it an ideal intervention model in MSME sector. Highlighted below are some of the salient features of the project that makes it unique, not just in terms of its achievement, but also the process followed. While Bhavnagar was an ideal cluster in terms of technical potential for energy saving and environment improvement, the team faced a very lukewarm response from the local industry initially as many other interventions in the past just ended up with a study report leading to the industry losing faith on such initiatives. So the first task for the team was to build trust and credibility for which the team followed a bottom up participatory approach engaging the local industry association and opinion leaders in the cluster in a very effective way. xiii

16 The results of the demonstration phase provided enough incentive for the local entrepreneurs to line up for implementing similar measures in their plants. The entrepreneurs not only paid the entire hardware cost, but also agreed to share the cost of engaging Allied Furnaces for technical backstopping/ knowledge provider. It is not very common to make a transition from a demonstration phase to an up scaling phase, as it happened in Bhavnagar. Results established so far in the replication phase has been very encouraging. The furnace efficiency has improved by 20% to 40% and the scale loss has reduced by 2%-5%. It has already been 3-4 months since the commissioning of the new furnaces and they are running quite well on sustainable basis. For the people engaged in this project, it was completely a riveting experience while making the journey through this cluster in taking along the industries to adopt a sustainable technology. Every new step of the projects involved different kind of adversities and the greatest challenges were to overcome those. It is very rare to get such cooperation in an MSME cluster. The environment has been made quite congenial with the kind of awareness that has been brought by the initiative and industries are now eager to participate in larger numbers. Now the way the dissemination material is prepared and ready for distribution, other cluster intervention is a real possibility even though the approach has to be customized as per the cluster dynamics which definitely can be taken care of. Apart from Jaipur, Raipur and Mandi Gobindgarh, there are lots of possibilities in the states of Kerala, Karnataka and Tamil Nadu which can be explored in coming days. One of the related idea which has been getting consolidated over the period of time is that the intervention so far has set a very good platform to generate emission reduction credits and can really give support to the project in future for extra financial incentive. This report provides lessons learned from implementing Energy Efficiency (EE) in Bhavanagar re-rolling cluster. Divided into three sections, it begins with recording the success story that is now written in the cluster which has successfully demonstrated the technology in three different industries of the cluster and many more in pipeline. In this section itself the report xiv

17 then goes on to present the pilot studies carried out under the project. The report highlights the energy efficiency implementation opportunities in the demonstrated units and perceived barriers impeding their adoption. The section concludes with a set of recommendations to enhance energy efficiency in the sector for the benefit of the implementing agencies. The second section is represented by the Japanese experts (Mr Sakae Tezuka and Mr Hitomi) who has worked in this project for last two-three years. Their understanding from the technology perspective of Japan is reflected in this section. The third section is dedicated drivers of Bhavnagar cluster who has given their perspective while going through this intervention. We sincerely hope that this effort to record the success story would help industries and other stakeholders to appreciate the importance and ways to implement such initiative in the Iron and Steel sector. Debajit Das Program Manager, Climate Change/Environment Winrock International India xv

18 Importance of Promoting End Use Energy Efficiency in India Introduction CTI Energy Efficiency Intervention Program in Gujarat, India aims to reduce the greenhouse gas emissions and improve the environment through energy efficiency intervention in Bhavnagar Rolling Mill Cluster in Gujarat, India. The program started with the survey to better understand composition and functionality of the steel rolling units in Bhavnagar Rolling Mill Cluster which assumes great importance for its energy intensive hub comprising of 60 operational rolling mill units that convert steel ingots to hot rolled bar and flat products. Almost all the units in the cluster are located in either of the two concentration pockets: Bhavnagar and Sihor areas, collectively called Bhavnagar Rolling Mill Cluster. With the help of industrial associations, in the previous stage four model units were chosen for conducting energy audit study for understanding the baseline situation and short, medium and long term options for energy efficiency improvements were evolved. The industries took the outcome positively and started implementing the short term which required little investments for implementation. Affordable and clean energy is a precondition for all economic activities and sustainable development. The energy demand in India is increasing rapidly by virtue of its fast growing economy and due to its sheer size of population. The energy usage quantum and pattern has also undergone a radical change over the past decade or so since the opening up of the economy. Energy committees that have brought out reports as far back as three decades ago have stressed the need for energy efficiency and conservation. However, even today the emphasis is on creating more supply options irrespective of the fact that nearly 30% to 50% of all energy produced is lost, either physically due to inefficiencies or financially due to theft/adulteration. The increasing global trade liberalization and growing global competition have made productivity improvement, including energy cost reduction, which is an important benchmark for economic success. Therefore, a paradigm shift in our approach to energy policy issues is needed - a shift from a supply dominated approach to an integrated approach incorporating a judicial mix of investment in supply side capacity, operational efficiency improvement of existing power generating stations, reduction of losses in transmission and distribution, end-use efficiency and renewable technologies. The policy goals and concepts will have to be shifted from energy conservation to energy efficiency, and from energy inputs to the effectiveness of energy use and energy services. Now that India is striving hard to attain energy security on a sustained basis, addressing the issues of the energy sector and promoting end use energy efficiency becomes all the more important. Objective The objective of this energy efficiency intervention which was initiated by International Centre for Environmental Technology Transfer (ICETT), Japan, is to identify a potential cluster where energy efficient technology can be demonstrated and subsequently replicated for up-scaling. In order to achieve the objective it was required to undertake a preliminary study of the critical energy intensive 16

19 sectors in the three target states of India. Initially three states namely Andhra Pradesh, Gujarat and Karnataka were selected for status survey and for understanding the scope for energy efficiency. Three focus industrial sectors were identified in each state based on a number of criteria which included both qualitative and quantitative factors. The idea was to choose those sectors in each state which have the following typical characteristics. The attributes which were considered while selecting the sectors are: q Sectors broadly falling in the medium-scale category q High energy intensity and high scope of improvement in energy efficiency q Sectors lagging behind in terms of technological development for improving energy efficiency q Pro-activeness of industry associations of the respective sectors q Number of units of the selected sector in the target state so as to have substantial replication potential for any demonstrated technology. Based on the above mentioned attributes, a cumulative assessment of the critical sectors in each state was carried out. Since most of the attributes required for selection of the appropriate sector are qualitative, hence WII s experience of working in the target states and sectors was utilized. The following sectors were covered as part of the present delegated research in each state. q Andhra Pradesh Pulp & paper Mini cement Sugar q Gujarat Rolling Ceramic Foundry q Karnataka Engineering & automobile Foundry Sugar 17

20 Chapter 1: Understanding the Clusters 1.1 Ranking of sectors in each state There is a felt need to prioritize the sectors in terms of interventions for improving energy efficiency and reducing greenhouse gas (GHG) emissions. Again, an exhaustive framework was developed and a number of critical qualitative and quantitative attributes have been considered while ranking the sectors in each state. These are the attributes which play a critical role in facilitating any kind of future activities to promote energy efficiency and GHG emission reduction. Each attribute was accorded different weightage considering the importance of the attribute in facilitating future activities. The attributes which have been considered in order to rank the sectors in each state are given below: q Sectoral energy conservation (EC) and GHG reduction potential q Willingness of industry to invest in EC technologies q Strength of the industry association in each sector q Availability of proven/commercial EC technologies for ready diffusion. First three attributes were accorded a weightage of 20 each on a scale of 70, whereas the last attribute was accorded a weightage of 10, depending on its relative importance in meeting the overall objective of future activities. The sectors studied in all the target states have been ranked based on the mentioned attributes. The final sectoral ranking as evolved were as given below: Sectoral Ranks I. Gujarat rolling sector II. Andhra Pradesh paper sector III. Andhra Pradesh cement sector IV. Karnataka sugar sector V. Gujarat foundry sector VI. Andhra Pradesh sugar sector VII. Karnataka foundry sectors VIII. Gujarat ceramic sector IX. Karnataka engineering sector The intent of developing an exhaustive framework is to prioritize states and sectors, where further focused interventions could be carried out. The ranking of states and sectors should broadly reflect those where substantial improvement in both energy and environment performance (in terms of reduced global as well as local emissions) is possible through focused demonstration of cleaner and efficient technologies, technical assistance, capacity building, fund facilitation, and hand holding support. It may be noted that ranking takes into account all the relevant quantitative and qualitative aspects and hence, it was expected that a future plan of action based on the above synthesis would be most effective in making the industrial sectors in the target states energy efficient, thereby resulting in substantial reduction in the emissions of greenhouse gases. As per the rankings Bhavnagar cluster was selected for further research and analysis. 18

21 1.2 Dynamics of Bhavnagar Rolling Mills Cluster Bhavnagar is a medium sized town in the state of Gujarat, located at a distance of approximately 200 km from Ahmedabad. The town assumes great importance from an industrial perspective since it is a big energy intensive hub comprising of a number of iron / steel re-rolling mills. The cluster comprises of about 60 re-rolling mill units which convert steel ingots to hot rolled bar and flat products. The raw material for the industry i.e. ingots are made by melting of steel scrap obtained from the nearby Alang port, which is a major ship breaking yard. The ingots are heated in a reheating pusher type coal fired furnace up to a temperature of around 1,200 C. The red hot ingots are then passed through various rollers a number of times to obtain the final products i.e. TMT bars, flats, special section bars etc. Of the entire manufacturing process, the reheating of ingots and the rolling of heated ingots into bars etc are the two major energy consuming processes. Almost all the units in the cluster are located in either of the two concentration pockets, which are: q Main town of Bhavnagar q Suburban area of Sihor, which is around 10 km from Bhavnagar. Both the areas, clubbed together are named as Bhavnagar Rolling Mill Cluster. The inventorisation exercise has revealed that there were 50 operational units in the cluster at the period of the study. The location of Bhavnagar and Sihor on the district map are shown in Figure 1.1. Figure 1.1: Location of re-rolling clusters in Bhavnagar and Sihor Figure 1.2: Distribution of rolling units between Bhavnagar and Sihor 19

22 1.3 Second phase activities Interaction with local industry associations To establish dialogue with the local rolling mills units, the approach adopted was en-route local industrial associations. Rolling Mills in Bhavnagar and Sihor have organized themselves into two association bodies which act as a platform for addressing common technical and economical issues among the units in their respective regions. These associations are Bhavnagar Steel Re-Rollers Association, Bhavnagar and Sihor Steel Re-Rolling Mills Association, Sihor. The Bhavnagar Steel Re-Rollers Association had 14 members while its counterpart Sihor Steel Re-Rolling Mills Association has 34 members, which have their respective units currently in operation. Besides these two associations, there are another association in Bhavnagar called Bhavnagar District Small Industries Association, which acts as an umbrella association for all the small-scale units operating in and around Bhavnagar. An extensive dialogue was initiated with the representatives of the local association so as to make them aware about the project and the specific objectives of the same. Discussions were also held on the tentative schedule of activities to be covered under the project, the roles of different partners and on developing a roadmap for the upcoming activities. Detailed discussions with these bodies also focused on understanding some process parameters of their rolling process, assessing the present status of energy conservation at cluster level and steps taken in the past to improve the energy efficiency. It was learnt that the overall picture of energy conservation measures taken in the past was not very bright and the status of energy efficiency in units were poor. As per the mandate of the state government, few units had previously got their energy consumption audited through government agencies Inventorisation of units in the cluster A detailed questionnaire was prepared for the purpose of inventorisation of the units in the cluster. With the help of industrial associations, almost all individual units were approached and were presented a detailed questionnaire form. The questionnaire sought details about the operating scale of the unit, the product mix, energy sources, average fuel consumption pattern, and previous attempts for energy conservation etc. along with the primary contact details of the units. The information collected by the inventorsation exercise has been compiled in the form of an MS Access database and is presented as a soft file document along with this report. Based on the information collected from the filled in questionnaires, some broad inferences have been drawn for the cluster. Some of the important parameters which have been derived from the information gathered during inventorisation exercise have been presented in Table

23 Table 1.3: Overview of Bhavnagar Rolling Mill Cluster Item Range of operation (production, TPM) Average production Average Coal Consumption Average Electricity Consumption Average Specific Energy Consumption Production / Consumption 45 TPM 1500 TPM 534 TPM 60 TPM 93 MWh / month 0.71 MkCal/ tonne; 0.07 Mtoe / tonne As can be seen from the above table, there is a large variation in average monthly production of the rolling mills. Average specific energy consumption has been calculated taking into account both the energy sources i.e. coal and electricity. Figures 1.3 and 1.4 show the percentage distribution of the units on the basis of their monthly production and coal consumption respectively. Figure 1.5 shows the share of each of these sources in the average energy consumption for the units in the cluster. Figure 1.3: Distribution based on average monthly production (TPM) Figure 1.4: Distribution based on average monthly coal consumption (TPM) 21 Figure 1.5: Percentage contribution of coal and electricity in overall energy consumption Identification of four units for energy and environment audit Based on the data collected in the questionnaire forms and after the discussions with both individual associations and the individual entrepreneurs, four representative units have been selected for energy and environment studies. Following factors have been taken into account for the purpose of selection of the demonstration units: q Production capacity q Product mix q Fuel consumption pattern q Recommendation by respective association q Outlook towards energy conservation

24 q Previous steps towards energy efficiency q Willingness and pro-activeness of the entrepreneur Efforts have been made to ensure that the selected units represent the whole cluster so that any activity in these four units can be easily replicated in other units. The selected demonstration units are: q Triveni Iron & Steel Industries Pvt. Ltd., F 28, Ruvapari Road, Bhavnagar q Steebars Re-Rollers, J 789, GIDC, Chitra, Bhavnagar q Vijay Steel, GIDC II, Sihor, Dist. Bhavnagar q Garg Casteels Pvt. Ltd., Village Vadiya, Sihor, Dist. Bhavnagar Joint Energy and Environmental studies in the four units Field visits were undertaken in the four units for energy and environmental research by joint team of WII and ICETT representatives. The visits were undertaken during August 7 13, The studies were conducted with a view to evaluate the production efficiency of the units, status of energy conservation and identify areas which are having scope for improvement with regards to energy conservation. The energy and environment audit methodology was planned and activities were carried out accordingly. The basic methodology adopted for the energy audit was to understand the process and to verify energy consumption inter-linkages in terms of thermal and electrical energy. The indicating parameters were then monitored and measured for the baseline status. The overall audit is categorized into three separate audits as described below: q Thermal energy audit Studies were undertaken to determine efficiencies of generation, distribution & utilization of thermal energies. Furnace efficiency tests were carried out to determine heat generation to fuel ratio. Fixed heating load, start up load & insulation losses were determined. Based on the above results, thermal energy balance is struck and based on the energy losses identified in the thermal energy balance, energy conservation measures are presented. The energy saving areas normally identified are: Improvement in steam / power generation efficiency, housekeeping measures, waste heat recovery, optimal choice of fuel, process optimization etc. q Electrical energy audit Energy billing patterns were analyzed for relevant penalties or fixed rates. Amperage, voltage, power factor & kwh on motors are measured. Actual running hours per batch or per hour outputs are observed. Electrical load analysis was carried out in order to see the trend in co-relation with rolling mills and furnace heating. The specific data collected at start up and stable condition were analyzed to understand the variation of electrical load and its consumption in terms of melting of the ingots and its effectiveness while passing through the rolling mills. q Environmental audit Environmental audit was carried out to assess various sources of emission and concentration of the same in co-relation to the operating practices of the units. Suitable monitoring plan and locations were identified to measure emissions both at ambient and flue gases. Coal sampling analysis was also carried out to know the level of unburnt coal both in the flue gas as well as bottom ash to assess the combustion efficiency and hence to co-relate with the emission levels to the environment. Possibilities of minimizing the same are then explored by taking suitable measures in the facilities and operating practices. 22

25 Chapter 2: Methodology 2.0 Typical production process of rolling mills in Bhavnagar A typical production process of a rolling mill unit is presented in Figure 2.1. Figure 2.1: Production process of re-rolling mills 23

26 The production process as depicted by the above chart is typical to almost all re-rolling units in the cluster. However, depending on the final product and production process, the above stated process flow is altered to suit the requirement of the industry. The following sections show the key features of the four industrial units selected for the study with respect to process variations, product mix and scale of operation: q Triveni Iron & Steel Industries Pvt. Ltd. Triveni Iron and Steel Industries manufacture special section products which vary from the regular sections in terms of complexity of shape. This requires a lot of lead time in changing the rolls of rolling stands so as to meet the requirement of the product. The unit procures raw material in form of ingots which are cut to size before feeding into reheating furnace with a production capacity of 40 TPD. q Steebars Re-Rollers Steebars Re-Rollers procure their raw material in form of scrap steel sheets from nearby Alang ship breaking yard. The sheets are sheared to size and then fed into the furnace for reheating. The production rate in terms of number of pieces is quite high due to smaller section products, mostly 6 mm round bars. The furnace length is also small as compared to other units as also the overall production process is quite unique. q Vijay Steel Vijay Steels use a raw material mix of scrap steel and ingots as per the end product requirement. Primary products are thin section channels and angles. The rolling mill of the unit is unique with a set of two automatic roller stands which increase the rate of production. Furnace has a capacity of 40 TPD and the average retention time of stock inside the furnace is around 6 hours because of increased length of furnace. Each lot of raw material is weighed before feeding into the furnace. q Garg Casteels Pvt. Ltd. The unit has an integrated steel melting shop equipped with 2,000 kva induction furnace along with the rolling mill. Special composition ingots are cast in the melting shop which is fed into the reheating furnace for rolling. The unit produces heavy section products and has installed two rolling mills which are used as per the end product requirement. This saves the time required for changing of rollers. The unit operates in the night hours to take advantage of the reduced electricity tariff. 24

27 2.1 Energy Audit Methodology The methodology used for the energy audit of the demonstration unit is presented in Figure 2.2. Figure 2.2: Energy audit methodology 2.2 Methodology for Scale loss study Scale loss refers to the material losses that occur due to formation of scale on the surface of hot metal during heating in the furnace at high temperature. The scale formation is primarily due to oxidation of surface of the material because of the presence of oxygen inside the furnace atmosphere. Scale loss has a significant impact on the economy of the process due to high cost of the material, and so 25

28 even small reduction in the scaling leads to substantial decrease in overall manufacturing cost. The scale loss is sometimes also referred to as oxidation loss or burning loss. Figure 2.3 describes the methodology adopted for figuring the scale loss at rolling mills. Figure 2.3: Methodology for scale-loss study By this way of running two sets of ingots, it is possible to measure how much of the scale is shredded off just after the furnace heating and how much is the remaining scale which gets removed in the 26

29 rolling process. However, it must be noted that there is no major additional scale formation during the rolling process. It is only the scale formed during heating that gets removed from the material while rolling. The above stated methodology was adapted to the onsite conditions as and when required. 2.3 Energy Conservation Measures On the basis of the detail Energy and Environmental Audit carried out in the above mentioned four representative industries of Bhavnagar cluster, possible measures that could be taken up in the units for energy conservation and bringing up energy efficiency was worked out. The methods covered a range from short-term and low investment options like putting proper temperature controlling systems, to long-term and investment intensive options like redesigning of the furnace and associated systems. The techno-economic feasibility of the possible measures was discussed along with each option. However, it needs to be mentioned here that these options have been presented here only as a list of possible options along with the savings associated Figure 2.4: Efficiency of the four units selected with each of them. Practical feasibility of each of these measures is discussed in consultation with representatives each from ICETT, WII and the industry in the later chapters. At the point of study time, Figure 2.4 presents the status of furnace efficiency in the units. 2.4 Short-term low investment options These measures include options which can be installed without any major alteration/modification in the existing systems and have investment requirement less than `5 lacs with a payback period of less than a year Installation of temperature controllers inside the furnace One common observation in all the units undertaken for study was lack of temperature monitoring systems for the furnace. In all units, temperature control is achieved by controlling the firing rate of coal. The temperature is estimated high, low or sufficient by the furnace operator at his own discretion and experience by looking at the colour of the heated stock. This is an unscientific method and causes unequal heating of charge. Also, it leads to overheating of the charge which leads to increased heat losses and increased scale loses. It was recommended that proper temperature measuring devices be installed at all relevant points in the furnace like different zones, flue gas duct, etc. This would not only help the furnace operator to correctly judge the temperature, but will also lead to reduction in heat loss and scale loss. It is estimated that such a measure would lead to a minimum energy saving of 3 4%. The following are the techno-economic measures as calculated for a representative industry, where highest operating temperature of furnace was recorded. The savings were calculated separately for material discharge temperature and the associated heat loss in flue gas due to high furnace temperature taking into account optimum excess air level of 20%. This is presented in Table

30 Table 2.1: Saving by installing temperature control system Saving on account of heating the stock Existing average working temperature of furnace 1,230 C Working temperature of furnace after installing controller 1,100 C Average production per day 37,120 Kg/day Saving in energy by reduced operating temperature 579,066 kcal/day Average boiler operation 300 days/annum Annual saving in fuel 30,638 Kg/annum Saving on account of reduced flue gas loss Average fuel firing rate Kg/hr Total air used for 20% excess air 9.5 Kg/Kg of fuel Mass of air supplied for combustion 3,089 Kg/hr Heat content of flue gases at existing condition 1,093,172 kcal/hr Heat content of flue gases after installing controllers 974,883 kcal/hr Equivalent saving in energy 118,289 kcal/hr Annual saving in fuel 75,104 Kg/annum Total fuel saving 105,742 Kg/annum Percentage fuel saving 9.06% Cost of fuel 6.00 `/Kg Annual monetary saving `6.34 Lac Investment Cost of control system `2 Lac Payback period 4 Months Controlling excess air inside the furnace Air is required for combustion of carbon present in coal (or any other fossil fuel). Depending on percentage of carbon in coal the stoichiometric amount of air required for combustion can be calculated. Stoichiometric amount of air is the minimum required for complete combustion of fuel. However, in practice, combustion is never perfect because of incomplete mixing of fuel and air. Therefore, to ensure complete combustion of fuel, a certain amount of air excess to stoichiometric amount is needed. For coal fired furnaces, the stoichiometric air required for combustion lies in the range of 7-8 Kg of air per Kg of coal and the excess air required for pulverized coal lies in the range of 15-20%. High oxygen content (more than 2-3.5% oxygen for 10-20% excess air) in the flue gas composition shows presence of high quantity of excess air, which adds to heat loss by consuming extra fuel and also by dropping the furnace temperature while entering. Flue gas studies carried out at two of the representative units showed high quantity of oxygen in flue gas composition. This was an indication of excess air being supplied to the furnace. Also, units where the combustion air supply was not in excess was also found with high oxygen in flue gas. This is a result of improper mixing of fuel and air. Some units already have a separate system for controlling air flow and coal feeding rate. Next was to interlink both the controls at pre-decided airfuel ratio. Also, one online flue gas analyzer could be mounted on the path of flue gas to check the composition and temperature of the gas stream. Table 2.2 presents the analysis of savings achieved by implementing this measure, calculated typically for Triveni Steels. 28

31 Table 2.2: Saving by controlling excess air inside the furnace Excess air being used for combustion 171% Corresponding dry flue gas loss 69.4% Optimum desired excess air level ( max ) 20% Corresponding oxygen level in flue gas 3.50% Corresponding dry flue gas loss 11.13% Reduction in dry flue gas loss 8.87% Hence saving in fuel consumption 8.87% Annual fuel consumption 1,167 TPA Fuel saved per annum 104 TPA Percentage fuel saving 8.9% Cost of fuel 6.00 `/Kg Annual monetary saving `6.21 Lac Investment (for combustion control system & combustion analyzer) `4 Lac Payback period 8 Months 2.5 Medium investment option Provision of waste heat recovery system Waste heat refers to the quantity of heat carried away by the hot flue gases escaping out of the furnace. These gases are generally in the range of C for typical reheating furnaces as installed in the four rolling units. The waste heat from the flue gases can be recovered and reutilized for heating combustion air. It is a thumb-rule that for every 20 C rise in temperature of combustion air, the efficiency gets improved by 1%, or saving of 1% in fuel consumption. Waste heat recovery systems (WHRS) are specialized according to type of use, and therefore, a detailed design for such a system needs to be worked out for this type of furnace. Also other particulars like location of WHRS, necessary alterations in furnace design etc also need to be worked out. However, using a general estimate, the saving calculations were worked out for this option as presented in Table

32 Table 2.3: Energy Saving by Installing Waste Heat Recovery System in furnace Average exit flue gas temperature 589 C Temp. of supply air for combustion in existing condition 29 C Temp. of supply air for combustion after installation of WHRS 200 C Rise in supply air temperature 171 C Total air used for 20% excess air 9.5 Kg/Kg of fuel Fuel firing rate Kg/hr Mass of air supplied for combustion 3089 Kg/hr Heat recovered from flue gas 155,595 kcal/hr Corresponding saving in fuel consumption Kg/hr Percentage saving in fuel consumption 8.46% Average furnace operation 12 hrs/day Annual saving in fuel 98,791 Kg/annum Cost of fuel 6.00 `/Kg Annual monetary saving `5.93 Lac Investment on installation `6.00* Lac Payback period 12 Months * Indicative Cost Installing proper capacity and proper design combustion system The combustion system primarily includes the burners, attached supply lines and associated accessories that are helpful in proper combustion of fuel by ensuring proper air-fuel mixing, fuel distribution, flame formation and propagation and so on. A proper design combustion system suiting to the capacity of the furnace is extremely necessary for optimizing the fuel combustion. The combustion system as seen in most of the units consist of burners made of simple pipes. This makes the fuel straight away being thrown into the furnace without any provision of mixing and being retained into the furnace chamber for a longer duration. Special burners available for firing pulverized coal need to be installed at all units. The following table shows the savings calculation for this option. The savings have been typically calculated for sample unit. Table 2.4: Savings by installing proper combustion system Average savings estimated by installing proper burners 5% Present fuel consumption rate 324 Kg/hr Heat input to the furnace 1,838,497.5 kcal/hr Reduction in heat input to the furnace 91,925 kcal/hr Average reduction in coal consumption per hour Kg/hr Average reduction in coal consumption per year 58, Kg/year Annual monetary savings `3.50 Lac 30

33 2.5.3 Increasing the length of preheating zone of the furnace Length of the preheating zone of furnace helps in extracting maximum heat from the furnace gases which preheat the material before it is actually heated in the furnace chamber. It also lowers the temperature of outgoing flue gases from the furnace. Table 2.5 shows the savings in fuel consumption that can be achieved by attaining a preheat temperature of 150 C of the material. Table 2.5: Savings in fuel consumption Temperature of material before feeding into the furnace 30 C Specific heat of the material (MS) 0.12 kcal/kg-c Temperature achieved by Preheating the material 150 C Material feeding rate 3,093.3 Kg/hr Heat input to the material 44, kcal/hr Fuel saving per hour Kg/hr Fuel saving per year 28,281.6 Kg/year Monetary saving `1.70 Lac Estimated Investment `6 Lac Simple Payback period 3.5 years 2.6 Long-term high investment option Redesigning of the furnace and associated systems The design of the present furnace is quite primitive and needs a complete change over from the present situation to a new and energy efficient design. At present, furnace installation is completely dependent on the local masonry resources. Furnaces are installed based on the experience of the local mason because of which new and modern techniques and materials are usually not incorporated into the design. Also, the associated systems like combustion air supply system, coal feeding system, combustion system including burners etc are far from being energy efficient. Also, many a times these systems deviate from the actual capacity required. In such a case, it becomes difficult to operate the furnace on maximum efficiency and productivity. The furnace design has to be modified in such a way as to provide maximum heat to the stock. Proper temperature distribution and temperature gradient inside the furnace need to be taken care of. Therefore, a complete shift over from the present system to new energy efficient and scientific design system is required. However, such a move will require a big investment of capital and major intervention in regular running of the plant, which may even lead to total closure of production activities for a few weeks. The cost economics of such a measure are possible only after the formulation of a detailed design are worked out in subsequent paragraphs Installation of Coal Gasifying System Gasification involves conversion of solid fuels like coal or biomass into gaseous fuel. Once the solid fuel is converted into gas, it becomes compatible for substitution of solid or liquid fuels in furnaces. Reheating furnaces of rolling mills, which consume furnace oil, can utilize gasification technology with great economic and environmental benefits. 31

34 Following points indicate that the producer gas operation should be more energy efficient and environment-friendly than pulverized coal operation: q Gas burns with more efficiency and cleaner flame as compared to coal. This leads to lower heat losses and lower dust emissions through stack, which are evident from the invisible emissions at the top of the chimney when the furnace operates on producer gas. q Biomass fuels have negligible sulphur. Even the sulphur content of Indian coals is much lower than that in furnace oil for a given energy output. Therefore, SO 2 emissions are expected to be much lower than that with furnace oil operation. q CO is normally a result of incomplete combustion. With better mixing of air & gas in gas burners, the CO is expected to be within acceptable limits. However, if the furnace is operating with insufficient combustion air, the CO emissions may go up. q When biomass is used for substituting pulverized coal, the CO emissions to the atmosphere are 2 reduced as the producer gas combustion has drastic reduction in net CO 2 emissions. The cost economics of gasifier installation was to be worked out with the gasifier vendors once the feasibility of one particular gasifier technology is freezed. 2.7 GHG emission reduction and CDM ability Many decisions of the United Nations Framework Convention on Climtae Change (UNFCCC) recognize the importance of energy efficiency; several Kyoto signatories have highlighted this as a key area for action; and the Marrakech Accords requested simplified approval procedures for smallscale CDM projects. Recent assessments estimate the potential savings from energy efficiency measures in developing countries alone to be between 30-45%; in energy-intensive industrial sub-sectors to be about 40% and 25-30% with a market potential of $50 billion and a payback less than three years. Also, low-cost opportunities lie predominantly in the hundreds of technologies and practices that are applicable to small- and medium-scale industries of the developing countries. The Bhavnagar cluster of re-rolling mills follows conventional and very traditional way of melting and rolling steel bars and through this study, an attempt is being made to bring down the energy consumption within limitations of the industrial operations which is influenced by market economy and other infrastructure. All the measures whichever is suggested for bringing down the energy consumption level, is expected to reduce the GHG emissions in terms of equivalent amount of avoidance of fossil fuel burning for the reduced energy consumption. Table 2.6 presents calculations based on the heating values saved and equivalent GHG emission reductions by each energy conservation measures. 32

35 Table 2.6: Energy conservation measures and the resultant emission reductions Measures Emissions reduction (tco 2 /annum) Installation of temperature controllers 190 Installation of waste heat recovery 177 Installation of proper combustion system 105 Increasing in length of preheating zone of the furnace 509 Redesign of furnace (long-term options) 982 From the above table even though the amount of certified emission reduction (CER) looks commercially not very attractive, however, the technology supplier with whom subsequent consultation was done for implementation of the measures are of the opinion that in actual, the quantum of saving will not only be high in terms fuel saving but also the scale loss which also carries out a major portion of the heat in both the rolling and melting process will be significantly reduced. In future course also when the implementation strategy is devised the approach were to be directed towards ensuring maximum multiplicity effect through the involvement of local industrial association and as such in there is a very good possibility of moulding this project as a viable Clean Development Mechanism (CDM) project by complying the requirements of UNFCCC as and when it progresses for success stories in the cluster and it will be important to record all the measuring and monitoring parameters to justify CDMability of the project in future. The possible CER revenue earning through the CDM project development will also go a long way to provide capital investment comfort to the entrepreneurs who are interested to take energy conservation measures in their industry. 33

36 Chapter 3: Implementation Plan 3.0 Implementation Action Plan 3.1 Comparative analysis of different possible long-term options As described in the previous sections, the energy audit study in four rolling units resulted in evaluating the specific energy consumption analysis along with the measurement and quantification of various heat losses. Different possible measures have already been laid down to minimize heat loss from the reheating furnace and improve its thermal efficiency. These energy conservation measures, depending on their energy conservation potential and amount of financial investment required had been categorized into short-, medium- and long-term options. The long-term options, having maximum impact potential and also most investment intensive, have been further looked into and an in-depth comparative analysis was carried out to identify the most suitable option out of the proposed one, keeping in mind the present energy input costs, current market trends of fuel prices and their future vulnerability. All these factors have a downstream effect on the profitability of the conversion process from scrap steel/ingots to steel bars, the final product, which is an ultimate source of inspiration for the entrepreneur to opt for any implementing energy efficiency improvement activity. Field visits were undertaken to a number of re-rolling mills operating in other parts of the country to study and verify the practical and actual operating parameters of the proposed energy conservation options in re-rolling mills where these were already implemented. Also, detailed discussions were held with various technology suppliers and subject-matter experts to determine the advantages and disadvantages of that particular technology within the present project boundaries. The feasibility and suitability of each of the long-term options was examined on both technical and financial grounds. The Table 3.1 shows the technical and financial comparison of various long-term options. All possible options have been compared on a set of common attributes, keeping same energy input as benchmark for comparison. However, it should be noted that the values for different parameters as stated in the table have been taken as best possible average of actual operating conditions as observed and measured at a number of places and therefore, their possibility to match the theoretical results is very limited. 34

37 Table 3.1: Technical and financial comparison of various long-term options 35 Particulars Efficiency of furnace heating Unit Pulverized Coal Energy input rate MJ/hr 6,802 GCV of coal MJ/Kg 20.9 Coal consumption Kg/hr 325 Gasifier + WHR FO + WHR Extending Furnace Length Remarks % 16 These values are taken for a typical reheating furnace in operation, as per energy audit study. GCV of coal is taken as an average value, as actual GCV varies over a wide range with each batch. Kg/hr 390 Gross coal consumption refers to actual coal Coal consumption (Gross) input to the furnace along with other handling and coal grade related losses. Energy input to material MJ/hr 1,054 Furnace efficiency improvement by redesigning the furnace (estimated) Flue gas temperature at exhaust Achievable combustion air preheat temperature at burners Efficiency improvement by waste heat recovery Improved Furnace Efficiency % Radiation and convection losses in the furnace are as high as 7%. Taking a conservative estimate of 2% energy saving by providing proper insulation and reducing surface temperature; 1% by providing proper burner location, burner orientation and burner loading; and 2% by controlling entrained air to the extent possible and by better furnace dynamics; all these factors add up to a minimum of 5% efficiency improvement of the furnace. C Estimated minimum flue gas temperature of 550 C at furnace exit. By extending the length of preheating zone to a notable extent, the flue gas temperature can be brought down to as low as 300 C. C NA NA The hot exhaust gas can be made to pass through a well designed waste heat recovery system having an overall effectiveness of 0.4 or more. % Taking an average volumetric flow of 2300 m3/hr of combustion air, the heat recovered from exhaust gases in form of combustion air preheat is of the order of 12% of the total energy input. This is at an average of 1% fuel saving for every 20 C temperature rise of combustion air. % Improved Furnace Efficiency = Existing furnace efficiency + furnace efficiency improvement + Waste heat recovery

38 Particulars Unit Pulverized Coal Gasifier + WHR FO + WHR Extending Furnace Length Remarks Fuel consumption for same Kg/hr (A) energy input to material (equivalent kg of coal) Fuel consumption for same Kg/hr energy input to material Any other fuel consumption Kg/hr Any other fuel consumption is stated here is to account for the additional fuel/energy, as associated with each of these options. ---(B) Total fuel consumption for same energy input to material (equivalent Kg of coal) Kg/hr (A) + (B) Overall Efficiency % Efficiency after considering any other fuel consumption Monetary savings by reduction in fuel consumption Monetary savings by reduction in fuel consumption Reduction in scale loss Monetary savings by reduction in scale loss ` /hr 609 1,335 1,504 1,114 Present landed cost of pulverized coal is `6.4/kg. Furnace oil used by the industry comes from nearby ship breaking yard with a landed cost of `13/kg. Lac ` / yr Lac ` / Total monetary savings yr Capital investment towards equipment Considering 12 hours operation a day for 250 days/annum. % Estimated values by considering existing operation at other rolling mills having already implemented such measures. Lac ` / yr Sum of monetary savings by reduction in fuel consumption and by reduction in scale loss. m New furnace ` Lac `75,000/ft length m Equipment cost ` Lac Gasifier/Recuperator Cost Operating cost of equipment/year ` Lac Over and above the existing operational cost for furnace Total investment ` Lac Simple Payback Period Years

39 The above table shows that considering current trends in fuel prices, switching over to furnace oil with a waste heat recovery system is the most attractive option out of all above. However, considering the future vulnerability of furnace oil prices, it is advisable to keep a provision for easy switching from furnace oil to any other cost effective fuel. Another exercise was carried out to estimate the required extension in furnace length to achieve exhaust gas temperature as low as 300 C. Temperature of hot gases inside the furnace was measured at a number of points located inside the pre-heating zone at fixed distance from each other. The temperature profile thus achieved was extrapolated at the same slope so as to estimate the extension in furnace length required for achieving the desired exhaust temperature. Table 3.2 presents the set of readings of measurements for the same. Table 3.2: Temperature of hot gases inside the furnace at different points from datum Point # Distance from datum (Point # 1) m Temperature, C Discussions with re-rolling units in Bhavnagar and Sihor The above comparison analysis was presented before each partner re-rolling unit in Bhavnagar and Sihor. Detailed discussions were held with individual re-rolling units so as to apprise them about the basis and details of comparison, and also the extent of suitability of each possible option for the particular rolling unit. The re-rolling units appreciated the cost benefit analysis of each option and provided their views about possible advantages and hindrances towards each option based on their own experience. Invariably, the units suggested that a system with easier fuel switching mechanism would be an ideal option. This led to finalization of long-term option as modification of furnace design coupled with a dual fuel firing system to switch over to furnace oil as fuel, as and when required. 3.3 Selection of two demonstration re-rolling units The re-rolling units in Bhavnagar and Sihor cluster can be broadly categorized in two ways i.e. based on location and based on raw material. This can be seen in Figure

40 Figure 3.1: Classification of re-rolling mills in Bhavnagar and Sihor clusters Out of the four partner rolling units, two rolling units were required to be selected for demonstration of energy conservation measures and implementing the long-term measures. As all the partner rolling units were willing to offer for undertaking the demonstration activities at their production sites, it was attempted to have a general consensus for selection of two final model units. A discussion panel was formed out of the representatives of rolling mills association of Bhavnagar and Sihor, representatives from individual rolling units, nominated members of associations and representatives from ICETT and WII. The panel discussed for the final selection considering a number of parameters which are provided below: q Location of rolling units q Kind of raw material q Availability of equipment, space and other facilities for demonstration q Willingness of the entrepreneur q Other aspects like scope of savings, outlook towards energy conservation, required changes in production scheduling and so on. Lastly, after achieving the general consensus on basis of above mentioned parameters, the discussion panel came out with the final selection of two demonstration units as follows: q Triveni Steels, Bhavnagar q Vijay Steels, Sihor The demonstration activities were to be carried out in the above mentioned two model units once the detailed furnace design for energy efficient furnace and detailed project design for implementation were available. 3.4 Efforts to provide financial incentive to the demonstration units Sincere efforts were put to provide financial assistance in terms of soft loan or subsidy schemes. From India, the existing schemes were analyzed and suitability was discussed for giving any such benefits to the industry owners and the process is still on. One of the major developments was at the initiative of ICETT and Clean Technology Initiative (CTI) through which United States Agency for International Development (USAID) was requested to see any possibility for financial incentive to the cluster 38

41 at Bhavnagar. USAID accepted our request and along with Private Financing Advisory Network (PFAN) made a site visit at the industrial clusters during first week of February 2009 and had detailed discussion with the management of M/s Vijay and M/s Triveni regarding the technology and their probable expenditure and their expectation from USAID for getting financial assistance. USAID had explained their model for financial assistance in terms of providing 50% collateral guarantee and also clarified various queries of the entrepreneurs. In order to ensure that as and when the financial package of USAID/PFAN is accepted by the industries and that the same is possible to be replicated in the whole cluster, finally a meeting was organized with the Industries Association of both Sihor and Bhavnagar to let them express their interest to USAID and PFAN. Ms Alison elaborated on the DCA model on offer and questions from various members were also answered to the satisfaction of the concerned parties. The support and enthusiasm from all the members including the entrepreneurs were very positive. The Mumbai meeting with ICICI bank was held in the presence of Ms Alison and Mr Peter Storey. In the meeting, Mr Storey explained the role of PFAN and Mr Somnath, Winrock International India talked about the project details and Mr Jaisingh Dhumal, Chief Manager, Project Development Group of ICICI Bank presented their various such activities and their modalities for taking up such financing. From USAID point of view, the DCA model was elaborated and issues regarding possible involvement from ICICI bank in the project were also discussed. As ICICI has its own limitations for funding in the current year, it was decided not to pursue this any further. 3.5 Identification of technology suppliers for implementation The demonstration rolling units in Bhavnagar were finalized and it was required to select a suitable technology supplier for supply of following deliverables: q Detailed Engineering Drawing of the energy efficient furnace q Bill of Materials for erection of furnace q Supervision during furnace erection and commissioning q Trial run of the furnace and fine tuning for optimal operation. A number of furnace technology suppliers were consulted and detailed discussions were held with each of them regarding the suitability of energy conservation options for re-rolling units in Bhavnagar, as well as the effect of smaller production capacity of the units on the devised measures. During the course of activities, it was observed that a majority of furnace technology suppliers had keen interest for catering to units with furnaces having larger production units. Table 3.3 presents the furnace technology suppliers that were consulted by WII for implementation of long term energy conservation measures in selected rolling units of Bhavnagar. 39

42 Table 3.3: List of furnace technology suppliers consulted by WII Furnace Technology Supplier Contact Details Simplicity Engineers Pvt Ltd B 99, Mayapuri, Phase 1, New Delhi Wesman Thermal engineering Processes Pvt Ltd National Institute of Secondary Steel Technology Technotherma Furnaces Pvt Ltd , Eros Apartments, Nehru Place, New Delhi G. T. Road, Mandi Gobindgarh, Punjab , Hallmark Commercial Complex, Mulund (W), Mumbai Allied Furnaces Allied House, Road No 1, Chembur, Mumbai CASE Group 117, Charmwood Plaza, Surajkund, Faridabad, Haryana Sycom Project Consultants Pvt Ltd VATIKA, 6 Kaushalya Park, Hauz Khas, New Delhi However, based on several factors, the furnace technology suppliers were again shortlisted from the above list. These factors are presented below: q Experience of the supplier in related technology q Continuity of the supplier in providing similar technology over last few years q Interest shown by supplier in providing technology for Bhavnagar cluster. Based on the above factors, the following three technology suppliers were shortlisted for detailed discussions. A joint visit was conducted by ICETT and WII team to each of these furnace technology suppliers for detailed discussions on various parameters relating to the implementation work to be carried out at rolling units in Bhavnagar. The ICETT team arrived in India on February 16th, 2009, for the purpose of joint visit to furnace technology suppliers. The following sections present the overview of discussions with individual technology suppliers. Allied Furnaces: A meeting with Allied Furnaces was held on February 17, 2009 at the office of Allied Furnaces in Mumbai. The meeting was attended by Mr N Rajgopala of Allied Furnaces, and representatives from ICETT and WII. The energy audit results and other information about the Bhavnagar rolling units were already conveyed to Allied Furnaces. This was further strengthened by the inputs of rolling mill expert Mr Tezuka in the project team. In the meeting Mr Rajgopala apprised the project team about the professional and technical capability of Allied Furnace, its prior experience in reheating furnaces and other technical possibilities/measures required to be undertaken along with the proposed energy conservation options. National Institute of Secondary Steel Technology (NISST): A visit was conducted to NISST in Mandi Gobindgarh, Punjab. The meeting was attended by Mr R K Bagchi, Director, NISST; Dr Rishi Srivastava, Sr. Dy. Director, NISST along with their colleagues and the project team. WII had already communicated the energy audit results and other information about rolling units to NISST. NISST, being a government institute of repute in the re-rolling sector and Mandi Gobindgarh cluster in particular, had already undertaken various diverse projects relating to energy efficiency improvement in rolling units in nearby locations. A brief presentation on these projects was made by Dr Srivastava on behalf of NISST. The project team visited one of the rolling units in Mandi Gobindgarh where 40

43 energy conservation activities had already been implemented by NISST in the past. During later part of the day, the project team visited Ludhiana in Punjab where energy conservation measures in smaller capacity reheating furnaces was already undertaken by WII under a separate project. Sycom Project Consultants Pvt Ltd: A meeting was held with Sycom Project Consultants to assess the technical and financial options as suggested by them. The meeting was held in WII s office at New Delhi on February 19, The meeting was attended by Mr Hajela and Mr Philip on behalf of Sycom. In the meeting, Sycom team apprised the project team about various projects undertaken by them in the steel re-rolling sector and also suggested various technical possibilities and modes of implementation of energy conservation measures. Sycom team also provided the financial offer for the same. As the individual meetings with each of these furnace technology suppliers were completed, it was the stage to decide the final technology supplier out of the three. 3.6 Selection of technology supplier for implementation Another meeting was held between the members of the project team on February 20, 2009 to finalize the selection for technology supplier for rolling units in Bhavnagar. A matrix was developed for ranking of individual suppliers by each member of the project team on a number of factors listed in the matrix. The sample matrix (Table 3.4) is presented below for reference. Table 3.4: Matrix for selecting a supplier Name of Company Company profile (A) Competence in taking up similar projects (B) Options analytical strength (C) Technical sustainability to take up Bhavnagar (D) On-ground implementation strength (E) Financial budget usefulness (till design) (F) Financial budget usefulness (till Commissioning) (G) Flexibility expectations to meet ICETT and WII workings (H) Overall Suitability (I) Allied Furnaces, Mumbai NISST, Mandi Gobindgarh Sycom Projects, New Delhi The project team filled in the points for each company on the basis of the guidelines. The financial proposals were also invited from each of the company so as to ascertain the financial component in the overall project implementation. However, as a possibility is still being envisaged for negotiations with companies on financial aspects, the commercial figures were omitted in the matrix for another set of readings (with other points remaining the same). 41

44 The final outcome of the evaluation exercise was based on the maximum highest criterion i.e. the company which is selected at highest points by majority was to be selected as technology supplier for implementing long term energy conservation measures in rolling units at Bhavnagar. Based on the results of evaluation matrix, Allied Furnaces, Mumbai was selected as the final supplier for furnace technology for rolling units in Bhavnagar. 42

45 Chapter 4: Activities Undertaken 4.0 Activities accomplished After prolong discussion and pursuance on all the technical options merit and broad cost economics, Vijay Steels was showing keen interest to be the demonstration unit for making further study and subsequently following activities were carried out- 4.1 Engagement of Allied Furnaces Pvt Ltd (AFPL) for supplying and installation of suitable furnace in the demonstration units Allied Furnaces was selected and further enquiry and discussions were made to bring down the financial implications of AFPL so as to fit within the budgetary provision of the project. Once the above was fixed, modalities for engagement were explored and a contract document was prepared to take care of the assurance for the energy efficiency component in the design and actual commissioning of the furnace and also to keep the business interest of the demonstration units intact. 4.2 Monitoring and review of supplied design in terms of integration and assurance of energy efficient technology and equipment The delivery schedule which was very much a part of the contract document was worked out in consultation with the entrepreneurs for their convenience of stoppage of production and taking up a shutdown. AFPL was taken to the site for visiting the selected model units to understand the actual facilities available and modification that might require for the case of retrofitting and the expectations of the owners of the units in terms of raw-material type and production capacity. AFPL collected all relevant data for the design of the retrofit/new design during the visit. The major propositions of AFPL were as follows: q Increase of furnace useful length: It was observed that in the units there was scope to increase furnace length by at least 10 feet. This would help in increasing the furnace capacity. q Zones of the furnace: Soaking zone alone: The soaking zone was proposed to be designed for independent capacity of T/hr, while the rest of the furnace would act as recuperative zone. For the capacity the soaking zone, burners would be on and supply heated/soaked material at the steady rate of T/hr. The fuel consumption is expected to be maximum Kg/hr with two burners only. The team strived to reduce it to about 225 Kg/hr. The aim was to bring the specific fuel consumption to around Kg/T of hot material withdrawal. q Soaking zone plus heating zone: These two zones under burner firing full blast would give the total guaranteed/higher production with the specific fuel consumption guaranteed. q All zones together: As discussed in connection with the increased, defined heat recovery (recuperative) zone, where there are no burners. Hot gases moving over the material transfer max heat to steel in this zone, so much so the exit gases leave the furnace at lower temperature. The residual/available heat and temperature in the gases at the exit are so low that the scope for installing a waste heat recovery system such as recuperator would not be viable and cost effective even if the gases were free from dust, ash and soot. 43

46 q q q Flat suspended roof: We propose changing the existing Arch roof with suspended type flat roof. This will enable us to minimize the free area above the charge in the pre-heating zone. The Arch roof leaves wide open area above the charge in the pre-heating zone which gives free space to hot flue gas from soaking and heating zones at approximately 1,000 C to cling to the roof and escape without exchanging heat to the charge. This results in poor heat transfer, hence the heat pick up by the charge is low and results in higher flue gas exit temperature. The exit temperature increases the chimney draft and thus drawing more flue gases out of the furnace, thus more fuel firing and air infiltration. The extra space available in Arch roof is up to 13% but in flat roof we can keep the gap as minimal as practically possible. When the gap is minimal, the hot flue gases are forced to pass through the charge and transfer maximum heat to the charge. Good heat transfer helps in double way, in reducing the flue exit temperature and reducing the fuel consumption to the extent of charge preheat. Further bifurcations of zones are practical and easy with flat roof only. Blowers: The team proposed a separate blower for combustion air requirement and for coal powder conveyance. The combustion air blower should be of low pressure and blower for coal should be of high pressure. Roots blower should be engaged ensure proper conveyance up to the furnace burner. By separating the air blower, both could be controlled independently. The screw conveyor of the coal feed can be controlled for control feed during firing turn down. This enables fuel saving when the furnace is idle due to some reason. This also prevents excess air in to high temperature zone of the furnace and thus minimizing oxidation and subsequently scale loss. The proposed arrangement can give a minimum of 1% reduction in scale loss inside the furnace. Multi fuel facility: Burners suitable for coal only were installed in the furnace. AFPL proposed to make provision for dual fuel burner mounting provision adjacent to coal fired burner. This opening should be closed from inside with refractory in order to avoid heat loss. Whenever it is required dual fuel burners can be procured and mounted in the space provided. C.A & Atomizing air piping needs to be done and the burner can be started without any modification in the furnace. Above findings were discussed in length with ICETT and Japanese expert Mr Tezuka and his comments were incorporated in the final outcome. The above outcome was shared with the entrepreneurs for their opinions and they gave a positive feedback over the technical outputs, however they expressed concerns on the financial investment for taking up the modification as for them the interventions proposed were a new thing and a kind of experimentation results of which are going to be shared in the cluster. Hence there was slight hesitation on behalf of the entrepreneurs and as Triveni had incurred a huge financial loss in the last financial year due to economic recession, they expressed their inability to take up the project for implementation. The second unit Vijay Steels however was keen to get the modification of furnace done under the project with some kind of financial incentives in terms of grants or subsidies for procurement of the hardware. Possible alternatives were explored for the same and JICA SIDBI was one such initiative which was given consideration. Another initiative of Gujarat State Government also was explored and a detail discussion was held with the District Industry Commissioner (DIC), Bhavnagar. 4.3 Taking up new unit as model unit As Triveni was not in a position to go ahead with the implementation, meeting was held with the industry association to select an alternative unit. Number of entrepreneurs were consulted and finally 44

47 Hans Industries was selected for developing as a model demonstration unit simply for their being an ingot based large capacity unit and their progressive nature of management in taking up energy efficiency initiative. To understand the baseline scenario, energy audit was carried out in the unit by WII and a preliminary visit was also made by AFPL engineers for collecting data to design the energy efficient furnace. In the meantime, fresh baseline data was also collected from Vijay Steels to accumulate data for any changed scenario since last time. 4.4 Fixing up the energy efficient design and assessment of energy efficiency that is expected from the new design AFPL submitted a design based on the survey and data/information collected and the detailed discussions they had with the entrepreneurs. Subsequently after its review and verification, AFPL also submitted the design drawings for both Vijay and Hans Industries. This includes detailed bill of quantity and specifications which were already consulted with the entrepreneurs and they were almost ready for procurement of various materials required for erection and commissioning of modified furnace. For Vijay Steels, as they requested for financial assistance JICA SIDBI line of credit was explored and detailed discussions were held with both JICA and SIDBI officials after which all necessary information was submitted. 4.5 Procurement of materials and equipments as per BOM Based on the Bill of Materials received with the design and drawing details of the furnace, the required materials/equipments were divided into following categories: q Furnace refractory and insulation: consisting of different kinds of refractory bricks with zonewise specifications, insulation material for lining of furnace walls and roof and other materials like fireclay mortar, castable etc. q Structural steel components for furnace: consisting of structural steel materials like C-channels, I-beams, MS plates etc for erection of furnace structure and to provide support for various furnace linings, different casting of holders and brackets for suspended roof structure. q Thermo-electric equipments and instrumentation: consisting of equipments like coal conveying blower, combustion air blower, thermocouples and indicators, etc. q Services of experts for various skilled tasks: consisting of fabrication work for furnace structure, installation of refractory and insulation linings etc. The procurement activities undertaken for each of these categories are mentioned below: q Furnace refractory and insulation: The furnace refractory specifications were provided by AFPL in the design documents itself. Refractory bricks of special specifications and geometry were required for the suspended roof structure. Following supplier was chosen by Vijay Steels for refractory as well as insulation material, based on the past business experience and supplier s reputation in the region. Bhavnagar Refractories and Ceramic Manufacturing Co. Danapith, Bhavnagar Phone: brcmc@sancharnet.in 45

48 The same company also supplied the construction materials like fireclay mortar, insulation bricks and so on. q Structural Steel Components: the following structural steel components were required for erection of furnace steel structure: I-beams as primary beams across furnace walls I-beams as secondary beams across furnace length C-channels for vertical support Cast iron holders and fixtures for suspended roof structure for holding the bricks and as fasteners MS plates for furnace wall panels and other structural components. Steel components like I-beams and channels were procured from local engineering market and directly from other manufacturers located in the region. The casting products were procured from a foundry in Rajkot city (about 170 kms from Bhavnagar) after developing the patterns for various fastener types as per the design provided by AFPL. MS plates and other fasteners and fabrication items were provided by M/s Vijay Steels from their in-house inventory. q Thermo-electric equipments and Instrumentation: As per the design of the modified system, an additional blower was required for conveying of pulverized coal to the burners. The specifications for high pressure blower were obtained from AFPL and also AFPL was requested to assist Vijay Steel in identifying a suitable supplier for the specified blower. The air blower was procured from the following supplier: Unimax Pollution Control (I) Pvt. Ltd. Solaris-I, D-145 Unit 1st Flr. Opp. L&T Gate No. 06, Saki Vihar Rd., Andheri (E) Mumbai Tel. No.: Fax No upcipl@gmail.com The combustion air blower was provided by Vijay Steels from their in-house inventory while thermocouples and temperature indicators were procured from engineering goods market in Bhavnagar and Ahmedabad city. q Fabrication and Masonry services: The energy efficient furnace being installed at the model unit is a pilot project for the region. Therefore, there was a clear lack of skilled services for steel fabrication and masonry work within the industry and the cluster. As a remedial measure, specialized fabricators and masonry teams were roped in to get the required skills and also to get the work completed within the stipulated time as per the design details. Specialized fabrication work services were provided by local steel fabrication firm with following contact details. AFPL was requested to identify a suitable firm for erection and masonry work for the furnace. The services were provided by engineering firm from Mumbai with following details: 46

49 4.6 Furnace erection activities Furnace erection activities were undertaken at Vijay Steels after closure of production activities on November 2, The existing furnace was brought to workable temperature by forced air drafts and the furnace was finally dismantled on November 4, Various important activities related to furnace erection work were: q Fabrication of primary and secondary beams, furnace wall panels for the extended portion q Dismantling of furnace pusher along with its foundation q Repair work in furnace side walls and hearth q Erection of extended portion of the furnace length q Sizing of furnace walls for the required height at various zones q Placing of structural components at specified location q Erection of new foundation for furnace pusher q Erection of new flue gas tunnel q Installation and erection of suspended roof q Fabrication of air supply and coal supply piping system q Fabrication and installation of burners q Installation of insulation material on furnace roof q Curing and treatment of pusher foundation 7 These activities can be best understood with the aid of photographs taken at the project site during various stages of furnace erection. Picture 1 2 show the fabrication work for furnace structure components. Picture 1 shows the fabrication of secondary beams. The fabricator is seen making the neck portion of the beams which is distinctly visible as the V-shaped component. Picture 2 shows another fabricator working on MS plate for fabrication of furnace wall panels. Picture 3-4 show an inside view of the furnace. The repair work is being carried out in furnace side walls for minor repairs and also to match the furnace height as per the design. Picture 5-6 show placements of various structural components of the furnace at the specified locations. Picture 5 shows location of primary and secondary beams of the furnace structure over the roof. These beams are the integral part of the suspended roof design. Picture 6 shows the placement of primary and secondary beams at the neck portion of the furnace. Primary beams make a V-shaped structure to define various zones of the furnace. 1 2 Pictures 7 10 show the activities for digging and erection of foundation for pusher. Picture 7 shows erection of pusher foundation at the charging end of the furnace. The pusher coordinates were finalized after completing the erection of extended length of the furnace. Picture 8-9 show various stages of pusher foundation activity. The pits in the brickwork are meant for locating the pusher foundation bolts and packing with RCC (concrete mixture) material for increased strength

50 5 6 8 Pictures show various stages of the erection work for flue gas tunnel towards the charging end of the furnace. Pictures below show various stages of the suspended roof installation activity. Picture 13 shows an inside view of placement of refractory bricks at the neck region which separates soaking and heating zones inside the furnace. Picture 16 shows top view of workers fixing the bricks on the beams with the help of fasteners. Pictures show the height adjustment from hearth to the furnace roof and the completed neck region of the furnace. Pictures show overview of the completed portions of the furnace Pictures show the fabrication and installation of pipe work in the furnace for air and coal flow and fabrication of burners. Picture 19 shows fabrication of coal conveying pipeline over the furnace roof. Separate lines were laid down for coal and air flow. Picture 20 shows fabrication of burners while pictures show installed burners at heating and soaking zone respectively q Furnace Erection Monitoring Activities: Various activities for furnace erection were monitored on a daily basis. Status report of various stages were prepared and discussed among the project team at the site to review the previous targets and to set the new targets for the next activities for implementation. The following shows a sample of such a status report

51 Status Report of Furnace Erection Work at Vijay Steels, Bhavnagar Activities completed till November 13, 2009 Activities Complete: q Fabrication work of beams, channels, back gate of furnace completed q Primary and Secondary Beams on Furnace Roof laid down, welded and bolted q Soaking and Heating Zone wall lining completed q Burner Blocks fixed and orientation also fixed q Furnace charging door and primary beams alignment done q Purchase order and advance payment for blower and refractory complete q Electric motor delivered to Unimax, Mumbai Activities in continuation: q Brick laying work of roof started and completed till soaking zone neck q Refractory lining of extended preheating zone continued q Pusher brickwork complete and foundation work continuing q Draft channel digging complete, erection continuing and curing to be done Activities Remaining q Completion of roof in heating and preheating zone q Hearth laying in soaking and heating zone q Hearth laying in the extended portion of the preheating zone q Locating and fixing of pusher and foundation work q Coal and combustion air pipe lining to be started and completed q Procuring of materials for piping work like valves, bends etc. q Fabrication of pipe structure and fitting q Delivery of coal conveying high pressure blower from Unimax, Mumbai q Location and fixing of instrumentation like thermocouple q Fabrication and installing of electric panel q Integrating the furnace, mechanical and electrical components 4.7 Furnace commissioning activities Furnace commissioning activities were started after completion of erection activities for all furnace components and subsequent curing of foundation and brickwork. The furnace was fired initially with firewood logs on November 22, However, due to major breakdown in the plant, not attributable to the furnace, the plant was shut down for a few days and commissioning activities resumed on December 1, As a part of commissioning activity, various operational parameters of the furnace, for example zone temperature, start up time, production output, coal flow etc are being recorded on a regular basis. As the plant starts approaching steady state, these furnace parameters are plotted for observing the variations over the stated duration. 49

52 Following graphs show the average temperature of respective zones, taken average from December 11-13, Figure 4.1: Soaking Zone Temperature Figure 4.2: Heating Zone Temperature Figure 4.3: Pre Heating Zone Temperature 50

53 Figure 4.4: Stack Gas Temperature Table 4.1 below presents the detailed furnace operation and specific fuel consumption analysis for the duration 10/12/2009 till 16/12/2009. Table 4.1: Furnace operation and specific fuel consumption details Date Production (Tons) Coal Consumption (Kg) Plant Running Time (hr) 10/12/ , /12/ , /12/ , Down time (min) Reason for downtime 10 Temp low 5 labour break 30 Mill problem 50 Coal feeder problem 5 Power problem 5 Mill problem 50 Mill problem 35 Mill problem 15 Mill problem 15 Mill problem 10 Mill problem 10 Mill problem 5 Mill problem 20 Mill problem 30 Mill problem 15 Mill problem 10 Mill problem 15 Mill problem 10 Mill problem 10 Mill problem 10 Mill problem 10 Mill problem 15 Coal feeder problem 15 Mill problem 20 Mill problem Specific Fuel Consumption (Kg/ Tonne)

54 Date Production (Tons) Coal Consumption (Kg) Plant Running Time (hr) 13/12/ , /12/ , Down time (min) Reason for downtime 10 Material jam 15 Material jam 5 10 Coal feeder problem 10 Material jam 15 Fan not working 10 Material jam 5 Material jam Material jam 10 Material jam 5 Labour break 15 Material jam 70 Power problem Size change 45 Mill problem 10 Power problem 110 Power problem 20 Mill problem Specific Fuel Consumption (Kg/ Tonne) The above details for specific fuel consumption have been plotted below in Figure 4.5. Figure 4.5: Specific Fuel Consumption trend for the period 10/12/2009 till 16/12/

55 As can be seen from Fig 4.1 to 4.5, the plant is approaching the steady state operation, however, the plant is required to run for longer duration with minimum breakdown time to ensure specific operational parameters. 4.8 Conducting detailed Energy and Environmental Audit Field studies were conducted for assessing the energy and environment performance of modified furnace. The scope of study included the folowing parameters: q Surface Temperature Study q Furnace Heat Balance q Scale loss Study q Environmental Performance Study All of the above studies were also conducted in the pre-demonstration phase of activities and the same methodologies were adopted for observation, measurements and evaluating the furnace performace in the post demonstration phase. The following gives detailed account of each of these studies conducted at the demonstration unit Vijay Steel during 5 8 January, Surface Temperature Study Surface temperature of the furnace was noted down after the furnace had reached the steady state operation. Figure 4.6 shows a schematic diagram of furnace temperature distribution at different zones of the furnace. Figure 4.6: Surface temperature distribution at Vijay Steels The above figure shows average surface temperatures of all three zones of the furnace. The measurements have been averaged out by dividing each zone into a number of sub-zones having almost equal surface area. The surface temperature in respective zones has decreased from 78 C to 67 C in preheating zone, from 103 C to 85 C in heating zone and from 143 C to 99oC in soaking zone. The reduction in surface temperature of the furnace shall be reflected in the reduction in radiation losses from the surface of the furnace this shall be calculated in later section Furnace Heat Balance The heat distribution inside the furnace was monitored by measuring the temperature inside each zone using a contact type thermocouple at regular intervals. Figure 4.7 shows the temperature profile of each zone of the furnace starting from furnace ignition up to the reaching of steady state. 53

56 Figure 4.7: Temperature of each furnace zone from start of furnace to steady state The above figure shows the temperature of each of the three zones during furnace startup time and during steady state from 5:30 AM till 7:00 PM. The entire heating cycle has been covered by monitoring the furnace temperature at regular intervals. Efficiency of the furnace can be calculated by following two methods: q Direct Method q Indirect method or heat loss method Both these methods require measuring of a number of operational parameters of the furnace. The indirect method has an advantage over the simpler direct method that various heat losses from the furnace can be quantified and accounted for. However, efficiency is calculated using both the methods and the results are presented along with the measured data in Tables 4.2. Table 4.2: Measured parameters related to furnace operation at Vijay Steels Parameter Unit Post demonstration Pre demonstration Ambient air temperature: (DBT) C Ambient air temperature: (WBT) C Material Temperature at feeding C Temp. of supply air for combustion C Average Oxygen level % Average CO level ppm Exit flue gas temperature C Average surface temperature -main body C Average surface temperature -front & back C Surface area - main body m Surface area - front & back m Material temperature at furnace exit C 1,148 1,080 Material Feeding Rate Kg/hr 5,880 2,820.4 Material Feeding Rate Kg/day 47,040 33,845 Fuel consumption per hour Kg/hr Fuel consumption per day Kg/day 3,564 3,168 54

57 The above data have been used to calculate the furnace efficiency in tables below. The following Table 4.3 presents the efficiency calculation by direct method. Table 4.3: Calculation of furnace efficiency by direct method for Vijay Steels Type of furnace Pusher type, Reheating Furnace Application of furnace Reheating of MS scrap for rolling Raw material under process MS scrap, sheared to size Parameter Unit Post-demonstration Pre-demonstration Production Capacity TPD Material feeding rate Kg/hr 5,880 2,820.4 Fuel Consumption rate Kg/hr Specific heat of the material kcal/kg C Material temperature at furnace entry C Material temperature at furnace exit C 1,100 1,080 Furnace efficiency by direct method % The above table shows that the furnace efficiency, as obtained by direct method, has increased to a level of 47% after the modification as to pre modification value of 28.6%. However, to account for various losses, the efficiency is also calculated by the indirect method in the Table 4.4 below. Table 4.4: Calculation of furnace efficiency by indirect method for Vijay Steels Parameter Unit Post-demonstration Pre-demonstration Measured O 2 in flue gas % Measured CO in flue gas ppm Excess air used for combustion % Corresponding CO 2 % Total air used for combustion Kg/Kg of fuel Heat loss due to dry flue gas % Heat loss due to moisture in fuel % Heat loss due to Hydrogen in fuel % Heat loss due to moisture in air % Heat loss due to CO formation % Heat loss due to radiation % Total losses % Furnace Efficiency % The above results have been plotted graphically in the Figure 4.8. The pie-chart represents the heat balance of the furnace at Vijay Steels. 55

58 Figure 4.8: Heat balance for reheating furnace at Vijay Steels It can be seen from the above analysis that the efficiency of the furnace has significantly improved to 48.8% from 14.7% after the modification. The rise in efficiency is due to reduction in dry flue gas loss, which in turn is achieved by reduction in excess air and complete burning of the fuel Scale Loss Study Scale loss study was carried out by the same methodology as for the baseline measurement. Since scale loss is an important parameter for the re-rolling mills, the results were ascertained by conducting more number of trials. Table 4.5 presents the results of scale loss study carried out at M/s Vijay Steels. Table 4.5: Results of scale loss study carried out at Vijay Steels Furnace heated Product Post-modification (Trial 1) Post-modification (Trial 2) Pre-modification Total Initial Weight* (Kg) Total Final Weight * (Kg) Difference (Kg) Difference (%) % Rolled out Product Post-modification (Trial 1) Post-modification (Trial 2) Pre-modification Total Initial Weight* (Kg) Total Final Weight * (Kg) Difference (Kg) Difference (%) *total weight of all sample ingots/bars The scale loss has been substantially reduced from almost 8% in the pre-demonstration times to just 5% after the demonstration activity. The reduction in scale loss is expected to generate significant monetary saving for the industry. 56

59 4.8.4 Environmental Performance Study q Ambient Air quality Monitoring: Monitoring of ambient air composition was carried out at two chosen points in and around the mill. Based on the distance from source of fugitive emissions i.e. the furnace, one monitoring point was located near the furnace to study the composition of ambient air at the workplace, while the other one was located near the storage area in front of administration building to study the effect of furnace operation on the nearby campus. Table 4.6 presents the results of the onsite monitoring and subsequent laboratory analysis of the ambient air samples collected at Vijay Steels. Table 4.6: Results of ambient air quality monitoring study at Vijay Steels Pre-modification Location Unit Post-modification Near Furnace Near Storage Area Result Pre-modification Near Furnace Near Storage Area Duration of monitoring Hr Sampling Procedure IS 5182 IS 5182 IS 5182 IS 5182 Suspended Particulate Matter µg/m Respirable Suspended µg/m Particulate Matter Nitrogen Dioxide µg/m Sulfur Dioxide µg/m The above table shows that considerable reduction of Suspended Particulate Matter (SPM) has been achieved in the working area as well as the nearby locations of the unit. The environmental performance of the furnace in terms of effect on ambient air quality has improved. q Stack Emission Monitoring: The draft of flue gas in the stack is an important factor which indicates the furnace performance. High temperature of flue gas inside the stack leads to higher heat losses. To monitor the draft and the emissions from the stack, the following related parameters were tested: SO2 NOx Particulate Matter Moisture Carbon Dioxide Oxygen Nitrogen Flue gas Velocity Flue gas Temperature Absolute Static Pressure inside the stack Stack emission was monitored during the study at Vijay Steels and the results of study and the results showed an increase of volumetric flow of flue gas through the stack, which translates into reduction in particulate and smoke emission from the furnace charging point. 57

60 q Unburnt Coal Analysis: Unburnt coal in the bottom ash of the furnace and in the particulates in the stack show incomplete combustion as well as carrying away of coal particles with the high velocity gas stream. Both these factors tend to bring down the efficiency of the furnace. Study was carried out for analysis of bottom ash of the furnace and the particulate matter inside the stack for finding the amount of un-burnt coal. Table 4.8 presents the results of the analysis. Table 4.8: Results of un-burnt coal analysis at Vijay Steels Particular Un-burnt Coal in Particulate matter in Underground duct Un-burnt coal in bottom ash collected from furnace during operation Value Unit Post Modification Pre Modification % % The above table shows significant reduction in the un-burnt coal both in bottom ash as well as the particulate matter in the stack. The un-burnt coal can be further reduced by optimizing the coal particle size from the pulverizer plant Observations q The surface temperature in respective zones has decreased from 78 C to 67 C in preheating zone, from 103 C to 85 C in heating zone and from 143 C to 99 C in soaking zone. q The furnace efficiency, as obtained by direct method, has increased to a level of 47% after the modification as to pre modification value of 28.6%. q The efficiency of the furnace, as obtained by indirect method has significantly improved to 48.8% from 14.7% after the modification. The rise is efficiency is due to reduction in dry flue gas loss, which in turn is achieved by reduction in excess air and complete burning of the fuel. q The scale loss has been substantially reduced from almost 8% in the pre-demonstration times to just 5% after the demonstration activity. The reduction in scale loss is expected to generate significant monetary saving for the industry. q The results showed that considerable reduction of Suspended Particulate Matter (SPM) has been achieved in the working area as well as the nearby locations of the unit. The environmental performance of the furnace in terms of effect on ambient air quality has been improved. q Volumetric flow of flue gas has increased through the stack, which translates into reduction in particulate and smoke emission from the furnace charging point and enhances better environment in the working area of the unit. q GHG reduction through the furnace stack has been reduced. The implemented technology is tested and found to be environment friendly as compared to existing technology in the cluster. q There is significant reduction in the un-burnt coal both in bottom ash as well as the particulate matter in the stack. 58

61 4.9 Dissemination Workshop in Bhavnagar The results of successful demonstration of energy conservation measures were disseminated to rolling units in the cluster by organizing a workshop titled Dissemination Workshop on Promoting Energy Efficiency for Small Scale Rerolling Mill in Bhavnagar on February 7, The preparatory activities for the workshop included preparation and circulation of invitation cards for delegates from the industry and special guests from the cluster. Extensive outreach activities were undertaken so as to circulate the information about the workshop. The workshop was attended by entrepreneurs from the rolling mill units from Bhavnagar and Sihor, government officials from departments of industry, MSME, banking personnel and financial analysts. Mr Rajubhai Rana, Member of Parliament from Bhavnagar, was invited as the chief guest of the event. Ms Vibhavariben Dave, Member of Legislative Assembly from Bhavnagar (North) and Mr Mehul Vadodaria, President, Saurashtra Chamber of Commerce and Industry were invited as Guest of Honour and Special Guest for the event respectively. Mr Somnath Bhattachajee, Vice President, WII provided a brief introduction of the project and gave introductory remarks for the event. It was followed by a presentation on Introduction of ICETT and its programatic activities in different parts of the world by Mr Yoichi Takaishi, Director of Global Environment Unit, ICETT, Japan. The presentation was followed by a special lecture by Mr Mehul Vadodaria where he discussed the present scenario of energy availability to the industry and emphasized on adoption of energy conservation measures and cleaner technology. It was followed by an addressing from Ms Vibhavariben Dave who first thanked ICETT for choosing the Bhavnagar re-rolling cluster for technology transfer for energy efficiency in rolling mills. Ms Dave discussed the role of policy and regulations in order to inherently bring in the efficient methods of production. Thereafter, Mr Rajubhai Rana delivered the inaugural address for the workshop and elaborated on the need of shift towards energy efficient technology in order to achieve cleaner environment and sustain the profitability of the production process by keeping the energy costs low. He also thanked ICETT and WII for carrying out successful research in Bhavnagar steel re-rolling cluster. The inaugural session concluded with closing remarks and a Vote of Thanks for the guests by Mr Qutub Kapasi, Secretary, Bhavnagar Steel Re-rollers Association and the participants dispersered briefly to assemble for the susequent Technical Session after the short tea break. The technical session started with a detailed overview of the entire intervention and research process by Mr Debajit Das, Program Manager, WII. It was followed by an informative and technically detailed presentation on an expert s view on re-rolling industry in Bhavnagar by Mr Sakae Tezuka, re-rolling technology expert from Japan. Thereafter, Mr Kenichi Shioya of ICETT gave a detailed presentation on future course of activities. It was followed by a presentation by Mr N Rajgopal of Allied Furnace Pvt Ltd who presented a detailed overview of the technology supplied along with the technological and financial vaibility of similar projects. The presentations were followed by an experience sharing session wherein different stakeholders shared their respective experiences and learnings during the course of project activities. Mr Muraribhai Gupta of Vijay Steels, Mr Mukesh Agrawal of Hans Industries and Mr Vikram Shah of Ace Consultancy briefed the participants from their point of view about various project components. A short felicitation ceremony was organized between the flow of activities to honour the untiring efforts and important contribution of Mr Muraribhai Gupta, Mr Vikram Shah and Mr Suresh Kumar 59

62 of Allied Furnaces Pvt Ltd. Thereafter, the house was announced open for technical and program related discussion and question & answer session presided by Mr Yoichi Takaishi, Mr Debajit Das, Mr N Rajgopal and Mr Muraribhai Gupta. A number of participants sought solutions to their queries regarding the future course of activities and technical details of implementation. The technical session was concluded with Vote of Thanks to all guests and participants by Mr Girdharbhai Solanki of Sihor Steel Re-rolling Mills Association. The workshop concluded with a visit to demonstration plant by the participants. 60

63 Chapter 5: Roadmap for Future 5.0 Future Course Of Action 5.1 Handing over the plant operations to the operational staff after giving adequate training for the efficient operation and maintenance Training modules will be developed for the grass root worker of the model unit keeping the set parameters and efficient operations and maintenance as base as sorted out in the guide book for the model units. The modules would be prepared in simple language for the understanding of the labor force who works in the furnace and rolling mill. Special emphasis will be given for understanding the work force in terms of the critical parameters of operation and maintenance and importance of maintaining energy efficient operations. 5.2 Detailed analysis of GHG emissions reductions and undertaking feasibility study towards CDM ability of the improved technology From the outputs of energy/environmental audits and the operational set process parameters, detailed analysis would also be carried out for GHG emission reduction being ensured by the energy efficiency interventions and also feasibility study will be carried, whether the project is possible to be build up as a CDM project vis-à-vis the UNFCCC requirement and Kyoto Protocol. Broad analysis of applicable methodology or suggestion of a new methodology for building up the CDM project will also be outlined in the feasibility report. 5.3 Workshop dissemination in Bhavnagar Once it is established that a successful and economically viable technological alternative is available for the rolling mills, then a policy platform would be created to impress upon the policy makers so as to facilitate a conducive environment for the replication of the technology. Representatives of local regulatory bodies, state government and Bureau of Energy Efficiency would be taken on board for the policy platform. Two interaction workshops would be carried out in the cluster which would have participation from all the stakeholders including the local entrepreneurs and policy makers. These workshops would serve the purpose of sensitizing all the stakeholders regarding the advantages of the demonstrated technology and would catalyze the process of replication. Conscious effort would be made to make the whole initiative self sustainable. Since the demonstrated system would have a quantum jump in operational efficiency over the conventional furnace, it would result in substantially reduced cost of production and hence better profitability. This would be win-win situation for all the stakeholders since whole of the initiative would ultimately be market driven and the replication of the technology would continue even after the withdrawal of 61

64 the intervening agency. The broader and more important objective of mitigating the GHG emissions from the rolling sector would also be met. The dissemination plan would also involve organizing exposure visits of prospective entrepreneurs to the demonstration site and focused group discussions and awareness raising campaigns to disseminate the benefits of adopting efficient and cleaner technologies in the rolling industries. 5.4 Setting up of future roadmap for replication of the energy efficient technology in the Bhavnagar re-rolling cluster The association of the Sihor and Bhavnagar re-rolling mills would be taken into confidence all along the implementation of the energy efficient technology at the model units so that the acceptability of the technologies sustains and the base for replication of the technology is created with a smoother proceeding in future courses. The future road map will be suggested highlighting the strategic requirements in terms of technical, financial and social need for ensuring multiplicity effect of the energy efficiency improvement in the re-rolling cluster at Bhavnagar. 62

65 Chapter 6: Dissemination and Replication In order to sustain the initiative by promoting replication of the demonstrated technology and also to research on future needs of energy efficiency in other sections of the rolling units, the developed roadmap was deemed important to be implemented in the cluster in a planned way. In this context, WII submitted a proposal requesting ICETT s support for undertaking the project titled Dissemination of Demonstrated Energy Efficient Technology in the Rolling Mill Cluster in Bhavnagar, Gujarat. ICETT continued the support to Bhavnagar rolling mill cluster and sanctioned the current phase of the project so as to create and implement a framework for sustained improvement and technology transfer in the small-scale rerolling sector. The project activities were started in April 2010 and this report presents the details of activities undertaken till now by the project team. The following specific activities were proposed to be undertaken in the planned initiative targeted to improve the energy and environmental performance of Bhavnagar rolling mills cluster during the financial year Discussion with Industrial Associations Industrial associations in Bhavnagar and Sihor have already been included into the project activities since the earlier phases of the project and all the milestones of the projects have been discussed with them from time to time. The same approach has been adopted in the present phase of the project as well. An interactive dialogue was initiated with the representatives of the local association so as to make them aware about the project outcomes of the last phase of the project and the specific objectives of the current phase. Discussions were also held on the tentative schedule of activities to be covered under the project, the roles of different partners and on developing a roadmap for the upcoming activities. The association expressed their happiness over the successful demonstration of the energy conservation measures with attractive cost benefit analysis. They stated that such intervention with successful results has been unprecedented in the cluster and that it shall go a long way in terms of perception of industrial community towards energy conservation. However, they also expressed concerns over sustaining the implementation and supported the proposed project activities for facilitating similar implantation in other units of the cluster. 6.2 Discussion with Gujarat Energy Development Agency The Gujarat Energy Development Agency (GEDA) is the State Designated Agency (SDA) for Gujarat and works closely with the Bureau of Energy Efficiency (BEE), the apex body for energy efficiency activities in India. GEDA is the nodal point for all policy matters relating to energy conservation, energy efficiency and renewable energy in Gujarat. 63

66 The coordinates of GED along with contact details of the nodal officer are presented below for reference. Mr R N Pandya Sr Project Executive Gujarat Energy Development Agency 4th Floor, Block No. 11 & 12, Udyog Bhavan, Sector 11, Gandhinagar Gujarat, India Ph: ; Fax: Rprasad58@yahoo.com; Web: Joint team of ICETT and WII personnel visited GEDA premises and held fruitful discussions with Mr Pandya. He was happy to learn about the successful outcome of the project and confirmed that the ongoing program falls in line with the broader mandate of GEDA. WII presented the documented details of the project to GEDA and requested to share their views about the program. Mr Pandya expressed GEDA s support to the project and committed their involvement in the activities as and when required. 64

67 Chapter 7: Results of the Intervention 7.0 Facilitation services to rolling units for technological upgradation As a result of dissemination workshop and discussions with local industrial association, several units in the cluster indicated their interest in participating in the replication process of the developed technology. Detailed discussions were held with each of these units regarding the modalities of the replication process, role play by various bodies involved, estimated capital investment, prevailing commercial scenario, time required for shut down, erection and commissioning and so on. The units studied the plan laid down for the replication activity and provided their suggestions on the same. The present chapter provides details on the selected units for replication and activities taken thereafter for providing facilitation services to the units for adoption of new technology. 7.1 Selection of rolling units for replication In the first phase of replication process, three rolling units in Bhavnagar were selected from among those that came forward. The selection process was carried out on the basis of a number of factors including but not limited to their readiness and willingness to take up energy conservation measures, availability of the units for proposed shutdown, committed production schedule and commercial scenario, etc. The details of selected units are provided in Table 7.1. Table 7.1: Selected rolling units for replication of new technology Name of the Unit Site Address Contact Person Raj Steels GIDC Vartej Sh Muraribhai Gupta Bhavnagar, Gujarat Shree Ramdev Steel Industries Survey No. 100, GIDC Phase 4, Sihor Ghangli Road, Vill. Vadia, Sihor Sh. Rajshekhar Iyer Sardar Steel Industries Survey No , Sihor Sh. Hemantbhai Ahmedabad Highway, Sihor Ghangli Road, Ghangli Replication work in each of the selected units was taken up as an individual project activity and the pre-demonstration research was taken up with each of the units so as to focus on individual unit s requirements. Of the three selected units, Raj Steels and Shree Ramdev Steel Industries were already into operation and the project was deemed feasible for retrofit of existing furnace in Raj Steels and installing new furnace in Shree Ramdev Steel Industries. The third unit Sardar Steel Industries is an upcoming unit in the cluster and the furnace design activities were started from the scratch. 65

68 Pre-demonstration diagnostic studies were carried out in the already operational units which included study of important operational parameters, product and raw material variations, detailed energy audits and scale loss study. The details about the methodologies and outcomes of the studies are presented in upcoming sections. Similar methodlogy for energy audit study and scale loss study was taken for the units. Monitoring in progress 7.2 Measurements and observations at Raj Steels The following gives detailed account of the diagnostic study conducted at M/s Raj Steels during April Surface Temperature Study Surface temperature of the furnace was noted down after the furnace had reached the steady state operation. The following Figure 7.1 shows a schematic diagram of furnace temperature distribution at different zones of the furnace. Figure 7.1: Surface temperature distribution for furnace zones at Raj Steels The above figure shows average surface temperatures of all three zones of the furnace. The measurements have been averaged out by dividing each zone into a number of sub-zones having almost equal surface area. The total heat loss due to radiation and convection because of high surface temperature of the furnace has been evaluated in later sections of this report Furnace Heat Balance The heat distribution inside the furnace was monitored by measuring the temperature inside each zone using a contact type thermocouple at regular intervals. The following Figure 7.2 shows the temperature profile of each zone of the furnace. 66

69 Figure 7.2: Furnace zone and Flue gas Temperatures Raj Steels The above figure shows the temperature of the heating and soaking zone rises up steadily till the maximum temperature is achieved and then converges towards 1100oC as the production progresses during the day. Also, the flue gas temperature cannot be recorded in the initial hours of firing as there is no flue gas flow through the underground flue duct. The entire volume of combustion gases escapes through the charging port while the flue duct shows ambient temperature. After first 4-5 hours of firing, the temperature in the flue duct started to rise, however, even during this phase a major fraction of the flue gas was observed to escape from the furnace charging point while very little of the flue gas passes through the stack attached with the furnace. Hence, the temperature and other flow parameters related with the flue gas in the stack have not been considered representative for calculations in this report. Efficiency of the furnace can be calculated by following two methods: q Direct Method q Indirect method or heat loss method Both these methods require measuring of a number of operational parameters of the furnace. The indirect method has an advantage over the simpler direct method that various heat losses from the furnace can be quantified and accounted for. However, efficiency is calculated using direct method only as representative measurements related to flue gas could not be gathered due to onsite conditions. The principle measurements and the results are presented in Tables

70 Table 7.2: Measured furnace operation parameters at Raj Steels Parameter Unit Value Ambient air temperature: (DBT) C 37 Ambient air temperature: (WBT) C 34 Material Temperature at feeding C 37 Temp. of supply air for combustion C 38 Average Oxygen level % 18.5 Average CO level ppm 9 Exit flue gas temperature C 287 Average surface temperature -main body C 81.4 Average surface temperature -front & back C 61 Surface area - main body m Surface area - front & back m Material temperature at furnace exit C 1,125 Material Feeding Rate Kg/hr 3,000 Material Feeding Rate Kg/day 30,000 Fuel consumption per hour Kg/hr 430 Fuel consumption per day Kg/day 5,160 The above data has been used to calculate the furnace efficiency by direct method in Table 7.3. Table 7.3: Calculation of furnace efficiency by direct method Raj Steels Parameter Unit Value Production Capacity TPD 30 Material feeding rate Kg/hr 3,000 Fuel Consumption rate Kg/hr 430 Specific heat of the material kcal/kg C 0.12 Material temperature at furnace entry C 37 Material temperature at furnace exit C 1,125 Furnace efficiency by direct method % 16.7 The above table shows that the furnace efficiency, as obtained by direct method, is calculated to be 17% which is on a lower side. The furnace heat balance as well as efficiency calculation by the indirect method cannot be performed as the measurements relating to flue gas flow are not representative due to onsite operating conditions Scale Loss Study Scale loss study was carried out by the methodology as mentioned before. Table 7.4 presents the results of scale loss study carried out at Raj Steels. 68

71 Table 7.4: Results of scale loss study carried out at Raj Steels Furnace heated Product Value Total Initial Weight* (Kg) Total Final Weight * (Kg) Difference (Kg) 5.62 Difference (%) 7.04 Rolled out Product Value Total Initial Weight* (Kg) Total Final Weight* (Kg) Difference (Kg) 7.04 Difference (%) 9.30 *total weight of all sample strips It can be seen from the above table that high scale generation of the order of 9.30 % takes place during the rolling operation. The scale generation is very high and required should be controlled by adopting better firing practices. A measurable reduction in scale loss can be observed if furnace design is adapted for low scale generation Observations q The surface temperature in heating and soaking zone is on a higher side. High surface temperature causes heat loss by radiation and convection. The surface temperature can be brought down by optimizing the temperature inside the furnace zones and by improving the furnace linings. q The furnace efficiency, as obtained by direct method, is 17% and is on a lower side. Furnace efficiency depends on a number of factors like combustion efficiency, heat transfer between hot gases and the material, adequate retention time inside the furnace and so on. Each of these factors needs to be addressed individually in order to raise the furnace efficiency and decrease the specific fuel consumption. q The Specific Fuel Consumption (SFC) in the furnace is found to be 143 Kg of coal per ton of product. q The escape of the flue gases from the charging point of the furnace causes difficult working conditions. Also, due to high velocity of escaping gases, the heat transfer to the cold entrant material is not efficient. q The scale generation in the rolling process is very high and is measured to be almost 9%. Such high scale loss also contributes to energy loss and monetary loss in terms of fuel and steel. 7.3 Measurements and observations at Shree Ramdev Steel Industries This section presents the detailed account of diagnostic study conducted at Shree Ramdev Steel Industries during April, Surface Temperature Study Surface temperature of the furnace was noted down after the furnace had reached the steady state operation. Figure 7.3 shows a schematic diagram of furnace temperature distribution at different zones of the furnace. 69

72 Figure 7.3: Surface temperature distribution for furnace zones Shree Ramdev Steel Industries The above figure shows average surface temperatures of all three zones of the furnace. The measurements have been averaged out by dividing each zone into a number of sub-zones having almost equal surface area. The total heat loss due radiation and convection because of high surface temperature of the furnace has been evaluated in later sections of this report Furnace Heat Balance The heat distribution inside the furnace was monitored by measuring the temperature inside each zone using a contact type thermocouple at regular intervals. Figure 7.4 shows the temperature profile of each zone of the furnace. Figure 7.4: Furnace zone and Flue gas Temperature Shree Ramdev Steel Industries The above figure shows the temperatures of the heating and soaking zone converge towards 1,230 C as the production progresses during the day. Also, the flue gas temperature decreases slightly during the day. However, as observed during the study, a major fraction of the flue gas escapes from the furnace charging point while very little of the flue gas passes through the stack attached with the furnace. Hence, the temperature and other flow parameters related with the flue gas in the stack have not been considered representative for calculations in this report. Efficiency of the furnace can be calculated by following two methods: q Direct method 70

73 q Indirect method or heat loss method Both these methods require measuring of a number of operational parameters of the furnace. The indirect method has an advantage over the simpler direct method that various heat losses from the furnace can be quantified and accounted for. However, efficiency is calculated using direct method only as representative measurements related to flue gas could not be gathered due to onsite conditions. The principle measurements and the results are presented in the following Tables Table 7.5: Measured furnace operation parameter - Shree Ramdev Steel Industries Parameter Unit Value Ambient air temperature: (DBT) C 33 Ambient air temperature: (WBT) C 30 Material Temperature at feeding C 33 Temp. of supply air for combustion C 35 Average Oxygen level % Average CO level ppm 60 Exit flue gas temperature C 436 Average surface temperature -main body C 104 Average surface temperature -front & back C 65 Surface area - main body m Surface area - front & back m Material temperature at furnace exit C 1,150 Material Feeding Rate Kg/hr 3,200 Material Feeding Rate Kg/day 32,000 Fuel consumption per hour Kg/hr 448 Fuel consumption per day Kg/day 5,376 The above data have been used to calculate the furnace efficiency by direct method in Table 7.6 below. Table 7.6: Furnace efficiency by direct method - Shree Ramdev Steel Industries Parameter Unit Value Production Capacity TPD 30 Material feeding rate Kg/hr 3200 Fuel Consumption rate Kg/hr 448 Specific heat of the material kcal/kg C 0.12 Material temperature at furnace entry C 33 Material temperature at furnace exit C 1150 Furnace efficiency by direct method % 17.6 The above table shows that the furnace efficiency, as obtained by direct method, is calculated to be 18% which is on a lower side. Also, various losses heat losses have been accounted in Table

74 Table 7.7: Calculation of various heat losses in furnace operation Parameter Unit Value Measured O 2 in flue gas % Measured CO in flue gas ppm 60 Excess air used for combustion % 105 Corresponding CO 2 % 9.66 Total air used for combustion Kg/Kg of fuel Heat loss due to dry flue gas % 36.0 Heat loss due to moisture in fuel % 1.5 Heat loss due to Hydrogen in fuel % 4.9 Heat loss due to moisture in air % 1.1 Heat loss due to CO formation % 0.0 Heat loss due to radiation % 2.6 Heat content in the material % 17.6 Unaccounted Heat Losses % 36.2 The above results have been plotted graphically in Figure 7.5. The following pie-chart represents the heat balance of the furnace at Shree Ramdev Steel Industries. Figure 7.5: Heat balance for reheating furnace - Shree Ramdev Steel Industries It can be seen from the above analysis that a substantial fraction of the overall heat loss is unaccounted because of flue escape from charging point of the furnace and other immeasurable parameters Scale Loss Study Scale loss study was carried out by the methodology as mentioned before. Table 7.8 presents the results of scale loss study carried out at Shree Ramdev Steel Industries. 72

75 Table 7.8: Results of scale loss study carried out at Ramdev Steel Industries Furnace heated Product Value Total Initial Weight* (Kg) Total Final Weight* (Kg) 69.6 Difference (Kg) 5.78 Difference (%) 7.67% Rolled out Product Value Total Initial Weight* (Kg) Total Final Weight* (Kg) Difference (Kg) 8.97 Difference (%) 11.78% *total weight of all sample strips It can be seen from the above table that high scale generation of the order of 12% takes place during the rolling operation. The scale generation is very high and required immediate attention Observations q The surface temperature in respective zones is on a higher side. High surface temperature causes heat loss by radiation and convection. The surface temperature can be brought down by optimizing the temperature inside the furnace zones and by improving the furnace linings. q The furnace efficiency, as obtained by direct method, is 18% and is on a lower side. Furnace efficiency depends on a number of factors like combustion efficiency, heat transfer between hot gases and the material, adequate retention time inside the furnace and so on. Each of these factors needs to be addressed individually in order to raise the furnace efficiency and decrease the specific fuel consumption. q The Specific Fuel Consumption (SFC) in the furnace is found to be 140 Kg of coal per tonne of product. q The calculation of various heat losses associated with furnace operation shows that almost 36% of the total heat input is lost for unaccounted reasons. This is primarily accounted to the escape of the flue gases from the charging point of the furnace as heat loss due to such escaping gases cannot be measured. q The scale generation in the rolling process is very high and is measured to be almost 12%. Such high scale loss also contributes to energy loss and monetary loss in terms of fuel and steel. 7.4 Facilitation/consulting services to replication units The selected units for replication for improved furnace technology approached WII for providing facilitation to take up the furnace installation activity with the technology supplier. WII also provided consulting services to the units in terms of technical information generation/ exchange between the units and the technology supplier. The present section describes each of the facilitation/consulting services provided by WII to the participating units Technical information generation and exchange The technology supplier for the improved furnace technology requires many preliminary data regarding the unit s operational parameters in order to work on the design development and fine 73

76 tuning of furnace design so as to suit the individual unit s requirement. However, the data logging and measurement practices at the units are either poor or completely absent. Also, the units lack the technical infrastructure and manpower to generate such data using instrumentation and support such systems. On the other hand, the design details provided by the technology supplier which are generally technically complex, are to be understood in detail by the units. The prescribed materials of construction and specification details of such material are put up in engineering terms. Such language and engineering details are not used in day to day operation of the rolling units. Hence, it is required to simplify the supplied information for better understanding of participating units. In the backdrop, WII took up the task of measurement and verification of operational parameters and provide these to the technology supplier. Field visits were undertaken to each of the participating units and onsite measurements were carried out. The information was compiled and provided to the technical service provider during design inception. It is expected that several such technical information generation visits would be required during and after the erection and commissioning of new furnaces Identification of material suppliers WII, in consultation with the participating units, helped them identify the suppliers for various components of Bills of Materials as provided by the technology supplier. This not only helped the units in faster procurement of products and services by different vendors at lower costs, but also helped the suppliers understand the immediate requirements of units in a better way. Indirectly, it helped the local suppliers which had been supplying material for the conventional design furnaces to become the Local Service Providers (LSPs) of their trade for the new design furnace system Coordination between stakeholders The units in Bhavnagar cluster are sensitive to the business scheduling as several months during the year are critical from the point of view of commercial aspects. Therefore, the furnace designs, erection and commissioning had to be scheduled in such a way so as to draw maximum benefit out of the business situation. The situation becomes critical as it is difficult to mobilize the technology supplier personnel and teams with all the material and service providers at the same time which effects their respective business commitments. WII coordinated the scheduling of personnel and resources among the various stakeholders so as to complete the design development, material procurement and inspection, furnace erection and commissioning activities etc within planned timeframe. This not only reduced the unproductive gaps within furnace erection schedule but also helped the stakeholders by shortening the respective downtime. 7.5 Evaluation of results and impact assessment Post demonstration performance assessment exercise was carried out at the units where erection and commissioning activities had been completed within the stipulated time frame. The following results were obtained for two replication units namely Raj Steels and Ramdev Steels. 74

77 7.5.1 Reduction in Specific Fuel Consumption The specific fuel consumption was measured in both the units as part of post demonstration performance assessment. It was observed that there has been a substantial reduction in specific fuel consumption in both the units, as presented in Table 7.9. Table 7.9: Reduction in specific fuel consumption after adoption of new technology Unit Specific Fuel Consumption (kg / Tonne) Pre demonstration Post demonstration Reduction in Specific Fuel Consumption Kg /Tonne % Raj Steels Ramdev Steels The above results have been shown below in Figure Increase in furnace thermal efficiency A direct indicator of the furnace performance improvement is increase in thermal efficiency. The furnace efficiency as calculated by direct method is compared for both pre demonstration and post demonstration scenario in Table Table 7.10: Improvement in furnace thermal efficiency Parameter Unit Raj Steels Ramdev Steels Pre Demo Post Demo Pre Demo Post Demo Production Capacity TPD Material feeding rate Kg/hr 3,000 3,500 3,200 4,500 Fuel Consumption rate Kg/hr Specific heat of the material kcal/ Kg oc Material temperature at furnace entry oc Material temperature at furnace exit oc 1,125 1,125 1,150 1,150 Furnace efficiency by direct method % It can be seen from the above table that furnace thermal efficiency has increased from 16.7% to 21.2 % in case of Raj Steels and from 17.6% to 29.2% in case of Ramdev Steels Reduction in Scale Loss Scale loss study was carried out in both the units by adopting the same methodology during predemonstration energy audit. The Table 7.11 presents the results of the scale loss generation in both the cases. 75

78 Table 7.11: Reduction in Scale loss Unit Overall Scale Loss (%) Reduction in Scale Loss (%) Pre demonstration Post demonstration Raj Steels Ramdev Steels The substantial reduction in scale loss is presented pictorially as Figure 7.7. Figure 7.6: Reduction in specific fuel consumption in the two units Figure 7.7: Reduction in scale loss in both two units 76

79 Chapter 8: Capacity building of stakeholders An important activity of the current phase of the project is capacity building of stakeholders including the floor supervisors in the rolling mills. This chapter describes the capacity building activities taken up in the cluster during implementation of the project. 8.1 Study of operation details from shop floor personnel In order to sustain the benefits arising from the newly installed technology, it is deemed important to train the shop floor personnel and their supervisors for best operating practices in the rolling mill units. The Japanese technical experts on panel with ICETT developed a questionnaire for clearer understanding of the rolling operation in the units. The questionnaire consisted of questions seeking the practices employed by the rolling mill managers and supervisors during day to day production activities. The questionnaire was circulated among the representative rolling units in the cluster namely, q J R Steels q Kali Ma Steels q S S Industries q Vijay Steels q Shree Ramdev Steel industries q Hans Industries The rolling units welcomed the move and provided the necessary information in the questionnaire with great enthusiasm. Several queries regarding the response of the rolling units were later on addressed by the units themselves. Picture 1: Site visit by team of ICETT and Japanese experts Based on the response of the questionnaire, joint field visits by ICETT, Japanese Experts and WII were planned and conducted in all the five rolling mill units wherein the questionnaire was circulated. Picture 2,3: Discussion with the Industry representatives 77

80 The experts took onsite measurements and interacted with rolling mill managers and supervisors in order to gain more understanding of the commonly employed practices and their shortcomings. The results of the field study were shared with the rolling mill managers and supervisors by conducting a workshop in Bhavnagar. The following section provides the details of the activity. Picture 4: Site visit by experts 8.2 First mini workshop for managers and supervisors The observations of the field visits to the rolling units were shared with the rolling mill supervisors and managers by inviting them to a workshop. The workshop was first of the two proposed workshops for training and capacity building of the shop floor personnel. Sh. Vinod Kumar Jangid, a leading industrialist in Bhavnagar cluster presided over the workshop and delivered the inaugural address. WII shared the project objectives and success story of the previous phase with the participants. The main attraction of the workshop were the interactive presentation made by Japanese experts, Mr Sakae Tezuka on general best operating practices in rolling units, and Mr Kiyoshi Hitomi on best operating practices in rolling process. They shared the Best Operating Practices for optimum and efficient rolling process with the participants and addressed their queries. Simulation questionnaire ICETT members, Japanese experts, WII team along with the participants of the programme 78

81 Based on the analysis of the information generated during the field visit to the industry, the experts developed another set of questionnaires specific for each of the industry visited during the first joint visit. The objective of the second questionnaire is to gather unit specific critical operational parameters in accurate details so as to develop the quantitative sets of Best Operating Parameters specific for each unit after providing the details in simulation program. The questionnaires have been circulated to the rolling units and the response is awaited. The results of the simulation will be shared and discussed with the industrial community in the next joint visit to the cluster. 8.3 Dissemination workshop for rolling units The successful results and learnings of the replication phase of the energy efficiency improvement program were shared with the rolling mills in the cluster by conducting Dissemination Workshop on Promotion of Energy Efficiency in Rerolling Units in Bhavnagar cluster on December 25, 2010 at Bhavnagar. The contents of the second of the two proposed mini workshops were also presented during the same workshop. President, Saurashtra Chamber of Commerce and Industry, presided over the workshop and delivered the inaugural address. WII shared the project objectives and success story of the replication phase with the participants. The main attraction of the workshop were interactive presentation made by Japanese experts, Mr Sakae Tezuka on general best operating practices in rolling units, and Mr Kiyoshi Hitomi on best operating practices in rolling process. The experts shared the Best Operating Practices for optimum and efficient rolling process with the participants and addressed their queries. 79

82 Energy Efficiency Intervention in Steel Rerolling Cluster in Bhavnagar, Gujarat Mr Vikram Shah CEO, Ace Consultancy Bhavnagar is fifth most populated city of Gujarat state and situated on west side of Gulf of Cambay. The main industries of Bhavnagar are manufacturing of plastic mono filament yarn, diamond cutting & polishing industries, salt industries, oxygen manufacturing units, steel re-rolling mills and induction furnace with some assorted chemical and engineering unit. Though the industries are following Government norms; the lack of transfer of new technology had resulted in declaring Chitra Industrial zone in Bhavnagar as one of the most polluted cluster of India three years before. Re-rolling mills and induction furnaces are energy guzzling industrial sectors. In Gujarat, more than 85% of the electricity produced from the thermal power stations is based on coal or lignite. Hydro power availability is very less due to irregular monsoon. While alternative energy is having quite less share in the total power used, energy used in Gujarat is having negative impact on ecological balance. To demonstrate a project of efficient re-heating furnace, the re-rolling mill cluster of Bhavnagar was selected as the re-rolling mill furnaces are heated by pulverised coal firing and they are also using enormous electricity in rolling process. Increase in efficiency of either furnace or rolling technique will directly or indirectly help in reducing greenhouse gases. So in the first stage it was decided to improve efficiency of reheating furnace so that carbon gases are reduced to decrease pollution level. The project has been sponsored by ICETT Japan and supported by Winrock International India. The rolling scenario in Bhavnagar cluster is different than the other steel industry clusters in India and abroad. Bhavnagar is at distance of 65 km from Alang Ship Recycling yard, which is the largest, such facility in the world. The related industries are developed in Bhavnagar, Sihor (26 km) and Mamsa (16 km) from Bhavnagar. The scrap material is available in different thickness and size. One option is to melt the scrap and make ingots/billets from the same which can be used to make structural steel product. This conversion is medium size industry and requires comparatively high investment for plant and inventory. 80

83 The other option is further shearing of the plates into strips and directly heat them in the reheating furnace and roll them to different sizes of structural steel angles and bars. The main disadvantage is the uneven size plates available for rolling. To use that material, a cluster of small size mills is developed by entrepreneurs of Bhavnagar. Due to typical material quality the reheating furnace size is small. As the standard design is not available for such reheating furnace and rolling mill, the design is developed by experienced professionals. Although it solves the purpose but most of these furnaces have poor energy efficiency, which results in extra burning of fossil fuels and increase in greenhouse gas emission. Frankly speaking, many agencies had tried to work on energy conservation in the rolling mills but they never reached the final stage. With the intensive pre-research and constant pursuance with the stakeholders like rolling mill owners, associations, designers etc, for the first time in history of the cluster a model unit was completed. The results are absolute positive and favourable. With the reduction in greenhouse gases, the increase in efficiency of rolling mill and the reduction in scale losses during heating and rolling; had made the project financially viable. I feel that the main achievement of the project is not the improvement of technology but change of mind set of rolling mill owners. The change is visible. Now almost everyone in the cluster thinks about furnace efficiency, use of coal and carbon emission. Whether they are working under the umbrella of this project or not but whenever they plan for renovation or modification or erection of a furnace; they ask supplier or contractor regarding efficiency or emission. This is a great achievement. A small revolution has started in thought process and we all know that the revolution starts from mind and then converts into implementation. In a way the green revolution has started in the cluster and will benefit all stakeholders and citizens of Bhavnagar with fresh and less polluted air. The technical knowhow from Japan via ICETT and the effort put by Winrok International India is the key factors for the success of the project. As a nodal agency, we had passed to gather through all the crest and trough during these years but with a commitment, unprecedented in Bhavnagar; both agencies had achieved the result. The next part is indirect reducing of greenhouse gasses by optimum use of electric energy. The main consumption of electricity is in rolling mill. Proper transmission of power and improvement in rolling technology will improve the efficiency of the system. In Bhavnagar cluster new design of rolling mill is drastically required. From the discussion with Japanese rolling technique expert, I understand that the data is simulated by them but to put the same in actual practice more field data is required. An ideal working of the mill, will indirectly help in reducing the harmful gasses. I wish that in the next year, we will benefit from more experts of this field. I heartily thank ICETT and Winrock International India on behalf of all the participants of the project and particularly from the people of Bhavnagar area for making a successful effort in improving their quality of life and hope that the project will be a sustainable one. Vikram Shah Ace Consultancy, Bhavnagar 81

84 Our Experience Regarding the Project - Vijay Steel Mr Murarilal Gupta CEO, Vijay Steels The spirit of entrepreneurship comes always with its inherent risk of success and failure. My journey with this re-rolling mill industry dates back to the 80 s when Bhavnagar and Sihor re-rolling cluster was just consolidating its operation and business. During this course our members have seen and faced lots of ups and downs and learnt many lessons which are the main capital for the entrepreneurs to their efforts on making this business sustainable and profitable. I am a Lions club member since many years. Many community projects have been completed and are ongoing at my behest. However, I was always in search of any opportunity to contribute in the re-rolling cluster and as such it is a great pleasure for me to get involved and participate in this energy efficiency intervention and do something for better quality of life for my workers and the society in large of Bhavnagar region. Actually it really clicked into my mind when WII members explained me the importance of energy saving and GHG reduction to save our planet from global warming so that the earth remains livable to our future generations. We are in re-rolling mill sector since long. The unbearable increase in oil price had forced us to go for pulverized coal based firing in our furnace. Being a small cluster and due to geographical corner situation, no major design consultant had worked in Bhavnagar. Though we are aware of efficiency of the furnace, no concrete work could be started due to lack of proper guidance. From the very first meeting I attended for introduction of project, I am appealed by the aim of the project. So from day one, I decided that by one or the other way we will associate with the project. Fortunately, the project coordinators had selected our unit as model unit. All the activities for dissemination of technology for reduction of greenhouse gases were carried out in our factory. The work started in 82

85 our factory a year before. The work related to project including designing, material procurement and actual field work was constantly monitored by WII and local coordinator under supervision of ICETT team and Japanese experts. In fact we had worked like a family during the work of model unit and enjoyed the whole experience. The results are shown in details in the final report of the project. Financially, no doubt the project is rewarding, but the real benefit in my opinion is reduction of CO 2 and CO, from the furnace emission. I am thankful to both the organizations for improving life standard of my workers and surrounding localities. We had also decided for energy efficient furnace erection in our group company M/s Raj Steel for the similar operation. It is a great pleasure and learning experience in working with all the related persons and I hope that we will get more assistance in rolling technology and improvement of electric efficiency of our factory from international experts in coming year. Murarilal Gupta CEO, Vijay Steels, Sihor 83

86 Our Experience with the Technology - Shree Ramdev Steel Shri Rajashekhar J Aiyar Proprietor Shree Ramdev Steel Industries Sihor rerolling mill association has always welcomed any effort that benefits the industry and society as a whole. As an office bearer of the association, I have always supported such activities that has the potential to contribute to the progress and well being to the society at large. From the beginning of the project, I am aware of the benefits of the project and sincerely appreciate the good effort on the part of ICETT, Japan and Winrock International India. All our units are small-scale enterprises manufacturing structural steel. The size of the end product and production is less compared to rolling mills of other clusters as raw material for them is ingot/billet while we are using ship recycling scrap. No standard design or qualified designer is available for such mills. We are aware about the losses in furnace and rolling and we are taking all steps to reduce the same, best to our knowledge but the perfect direction based on technical engineering expertise was lacking. The ICETT and WII initiative has come to us as a saving respite as our entrepreneurs can hardly afford such technical expertise and also in the change in mindset. I was always looking for better technology and better work practice for more energy efficient equipment and for improved atmosphere for my workers. After the workshop and visiting the model unit, I had decided to go for renovation of our furnace with new design. The improved technology will not only reduce the coal consumption but also reduce greenhouse gasses considerably. The work of renovation started in second phase of the project in Bhavnagar cluster. The designer M/s Allied Furnace had furnished the design for the furnace. Some onsite modification in design was required, particularly in coal feeding system. The same was complied with our indigenous experience. The work was monitored by all the concerned stakeholders and we are thankful for that. The ultimate result is more than the expectation and we achieved good energy efficiency, decrease in carbon emissions and remarkable reduction of scale losses. I wish that such project with wide span of activities including capacity building, product quality improvement and world class trade practice introduction should be continued with international collaboration with esteemed organizations such as ICETT from Japan and WII from India, which will not only enhance the productivity, business competitiveness but also change the face of this age-old cluster. For Shree Ramdev Steel Industries Shekharbhai Aiyer Treasurer: Sihor Steel Rerolling Mills Association 84

87 Chapter 9: Fundamental Technologies on Steel Rolling 9.1 Necessary Conditions for Rolling Steel Material Necessary Conditions and Countermeasures to realize the necessary conditions for steel rolling mill are summarized in Table 9.1. Mr Sakae Tezuka Table 9.1. Necessary Conditions for Steel Rolling Mill Item Necessary Condition Countermeasures to Realize Necessary Condition Product quality Productivity Primary product yield Energy efficiency Environmental effect Safety 9.2 Product Quality 1) Mechanical properties and metallurgical properties which are Uniform and appropriate to aimed values 2) Uniform shape with dimensional accuracy which is within aimed accuracy 3) Good surface quality Producing rate appropriate to sales order with least human power Maximum yield with least fallen-out scrap and scale loss Least energy consumption for good quality, appropriate productivity, good environment and safety Least pollution without vibration nor noisy sound Least danger of firing, explosion and pinching 1) Reduction ratios as well as rolling temperature appropriate to aimed rolling pass schedule 2) Accurate mathematic rolling control model 3) Good rolling mill facilities maintenance Automatic control with measuring instruments and computer system Rolling pass schedule, heating and cooling Rolling pass schedule and stable rolling operation Oil seal & dust collector, roll coolant, lubrication Operating procedures and facilities maintenance Mechanical Property Carbon steel (Figure 9.1) is composed of both Iron and Carbon. But if the Carbon portion ist oo large, due to its coarse metallurgical structure it becomes hard and brittle. In order to improve mechanical property, and rolling work, Carbon portion needs to be of proper range and the finishing temperature of rolling should be higher than the phase transformation line, along which Carbon steel changes phase from Austenite solid solution to Ferrite solid solution. It is roughly a straight line between two points of (910 C, 0%C) and (723 C, 0.80%C). Accurately the phase transformation line depends upon Carbon portion in the steel. 85

88 In case of steel with other metallic components, the transformation phenomenon becomes more complex. In the usual rolling process, rolled product is naturally cooled from higher temperature (than the phase of Austenite g), in order to obtain fine grain structure as well as to release strain which is caused by casting and rolling. In Controlled Rolling and Thermo Mechanical Treatment, rolled material is quickly cooled with high cooling rate just after rolling is finished. It is effective to obtain high strength as well as toughness and ductility without addition of alloy components during steel making process. Representative mechanical property of rolled steel is Strength, which is composed of Tensile strength, Fatigue strength (or Yield strength) and Creep strength. Though strength of Ferrite - Pearlite steel depends upon Carbon concentration, since too high Carbon concentration makes steel brittle, when high strength is necessary, such alloy components as Mn and Si are added. When high strength and good welding properties as High Tensile Strength Steel is necessary, material is rolled by controlled rolling method or accelerated cooling method. When re-heated material is exposed under high temperature for a long time (t), grain diameter (d) is shown by the following equation; d= Kt n (9.1) where, d: Austenite grain diameter, K: constant coefficient, t: time for which the material is heated n: grain growth rate (in the normal case, n is about 1/6) Controlled Rolling Figure 9.1 Metallurgical Phase Diagram of Carbon Steel Controlled Rolling process is a rolling technology to *1 obtain high ductility as well as high tensile strength, under low using temperature. The mechanical properties of the material made by Controlled Rolling process are obtained with high tensile strength and ductility without addition of alloy contents but with thermo-mechanical treatment. Throughout the Controlled Rolling process, both material temperature and reduction ratio are controlled from the entrance of re-heating furnace to the exit of cooling bed. The reduction ratio is shown as follows: Reduction Ratio= Exit Cross Sectional Area/ Entrance Cross Sectional Area The rolling temperature of Controlled Rolling is usually under 900 C. Figure 9.2 shows the affect of rolling temperature to mechanical properties of the rolled product. Though reduction ratio in temperature ranges over 750 C, it does not effect the mechanical properties, but reduction ratio under 750 C significantly does. In order to effectively carry out the Controlled Rolling, the following three measures are significant: (1) Low temperature re-heating to make smaller initial grain diameter (2) Shorter time processing to prevent Austenite grain growth 86

89 (3) High reduction ratio in lower temperature than re-crystallizing temperature Finishing Temperature of Rolling>Ar3 Point Temperature Figrue 9.3 shows some examples of actual discharging temperature in hot strip rolling mills in Japan. It includes discharging temperature of mild steel and high tensile strength steel. Discharging temperature of both steel grades is negatively proportional to product thickness. It means that in order to obtain appropriate material property, discharging temperature for thinner product needs to be higher than one for thicker product due to cooling down during rolling. It means that more the product thickness is, lesser Rolling Force is enough, and shorter rolling time is enough to obtain product dimension. Dimensional Accuracy Customers use the rolled products as material for their own products such as machine parts, based upon the dimensional accuracy of the rolled products. The accuracy of the rolled products is controlled by the following: q Mechanical accuracy of rolling gap adjustment q Mechanical rigidity and robustness of the rolling mill stands q Accuracy of material temperature with measurement and estimating calculation q Accuracy of rolling pass schedule (Draft Schedule) q Dimensional accuracy and Surface condition of roll If width of the rolled material is assumed constant during rolling process, the relation among change of the Exit Thickness, Roll gap, Deformation Resistance of Material, Rolling Force and Rolling Mill Constant are as follows: P= M*(h-S 0 ) (9.2) P= b*k m *Q r * R'*( H h) (9.3) Figure 9.2 Relation of Rolling Temperature vs. Tensile Strength and Yield Strength *2 Figure 9.3 Product thickness vs. Discharged temperature *2 Where P: Rolling force (N) M: Mill Constant (N/mm) h: Material thickness at the exit of rolling mill (mm) S 0 : Roll gap without rolling force (mm) b: material width (mm) k m : Averaged Deformation Resistance of Material (N/mm 2 ) Q r : Rolling Force Function R *: Roll Radius which is flattened by rolling force (mm) H: Material thickness at the entry of rolling mill (mm) By substituting Equation (2) to Equation (3), the exit thickness h is calculated. 87

90 Fig 9.5 shows the relation. In Figure 9.4, Equation (3) shows elastic deformation of rolling mill which is displayed in line A, and the plastic deformation of rolled material is shown in line B. The material thickness at the exit of the rolling mill is obtained as the cross point of line A and line B in Fig 9.5. At that time rolling force is P. Figure 9.4 Thickness determination 1 *2 When the deformation resistance changes, it means that in Fig 9.5, line B changes to another line B. As a result of the change of the deformation resistance material thickness at the exit of rolling mill changes from h to h. The rolling force changes from P to P a. If the plastic deformation resistance changes due to material temperature change, roll gap needs to be adjusted from S 0 to S 0, in order to obtain the aimed thickness h at the exit of the rolling mill. This relation is described as the following: S 0 - S= P Pa M (9.4) On the other hand, if the entry thickness changes from H to H, as shown in Figure 9.5, the plastic deformation of the material, and as a result of that the exit thickness changes from h to h. In this case in order to obtain aimed thickness, it is enough to set the roll gap from S to S 0. At that time rolling force becomes P 0. In Figure 9.5, S 0 - S 0 = P0 P M (9.5) Figure 9.4 and Figure 9.5 show the Thickness Determining Principles that if rolling force is measured with some load cell, when deformation resistance or entrance Figure 9.5 Thickness thickness of rolled material changes, roll gap can be adjusted so as to get rid of the determination 2 *2 deviation of exit thickness by cancelling the rolling force deviation. If load cell, controller and roll gap adjusting mechanism are installed, exit thickness can be automatically controlled. In order to obtain accurate exit thickness, Entry Thickness, Rolling Gap without rolling force, Rolling Mill Constant, Roll Radius should be maintained at stable state. In addition, deformation resistance should be accurately estimated, and if possible the deformation resistance is better to be stable by progressing rolling operation in a short time. Mill Constant M and Deformation Resistance Km can be determined by both of theoretical study and experimental study. Especially in order to study them, load cell and roll gap measuring gauge are necessary to install. In addition thickness is necessary to measure before and after each rolling pass. The thickness measurement is enough for on line or off line. Deformation Resistance will be discussed again later. Surface Quality Scale Generation Major defects on the surface of Rolled Steel Product are Scale defect and Slip defect. Scale defect is caused by non-uniform removing of scale from the product surface. So called Scale is Oxidized material of iron or some other kind of metal. 88

91 Figure 9.6 shows Oxidizing time dependence of grown thickness of Oxidized material in some steel grade. Such characteristics as Figure 9.6 depend upon each steel grade. The most external scale is composed of Fe 2 O 3, which is least portion in whole scale layer. Scale in the middle layer is composed of Fe 3 O 4, this portion is middle of whole scale layer. Most of scale is internal FeO layer, the growth rate of which is fast in the earlier stage and slower in the later stage. The most external layer of Fe 2 O 3 is an inert metallurgical structure, prevents more progress of Oxidization of middle and internal layers. Figure 9.6 Growth of scale *2 Figure 9.7 shows the equilibrium diagram between Iron and Oxygen of some steel grade. This diagram can be commonly applied to every steel grade. Surface defect due to scale is mainly affected by Mechanical Properties and Contacting Force of the scale layer. Mechanical properties are affected by Temperature, Chemical Components, Portion of Impurities, Grain dimension, and Air Cavity portion, Boundary Condition between scale and mother body and Internal Stress. Fracture Strength of scale under ambient temperature increases in accordance with Oxygen portion in the scale. FeO has lowest strength of three kinds of scale layer, on the other hand Fe 2 O 3 has the highest strength of the three. Figure 9.7 Equilibrium The mechanical properties are strongly affected by scale thickness. Generally the between Fe-O *2 thinner the layer grows the stronger the scale becomes. Regarding Contacting Force, in addition to the effects of Strength and Plastic Deformation Property, Stress between scale and mother body is significant. In order to decrease surface defect due to scale, it is important to prevent scale generation during reheating in the furnace, and to smoothly remove scale layer from mother body of the heated Material. In order to prevent scale generation, it is effective to decrease the Multiplication of Heating Time Oxygen Portion in the Combustion Gas and Heating Temperature. It means that it is effective to heat the material with low Air ratio and with appropriate temperature in a short heating time to the appropriate temperature. On the other hand it is also important to remove once generated scale on the surface of the heated material. In order to remove scale, two kinds of scale remover are used. One is mechanical scale breaker. The other is hydraulic de-scaling device. The mechanical scale breaker is principally vertical rolling mill. The hydraulic de-scaling device ejects pressurized water to the surface of the heated material. Surface Defect by Abrasion by Skid In pusher type re-heating furnace, especially in the soaking zone with high temperature, the bottom surface of the heated material becomes easily damaged from abrasion by skid pipe or skid runner with material s own weight. It is caused by the material becoming soft in the high temperature circumstances. 89

92 9.3 Temperature and Deformation Resistance of Rolled Material Temperature of rolled material changes during re-heating, transportation and rolling. In the re-heating furnace the material is heated with some kind of fuel to get the appropriate temperature for rolling. After being discharged from the re-heating furnace, the material is cooled during transportation and rolling. The major causes of material cooling are as follows: q Radiation and Convection with ambient air q Convection with roll coolant (water) q Conduction with transferring machines and rolls q Convection with cooling water for Thermo-Mechanical Treatment Though the material temperature in these cooling processes can be calculated with general heat transfer theory, in detail the temperature needs to be experimentally obtained in accordance with shape and dimension of the material, moving speed, cooling condition etc. Figure 9.8 shows an example of Temperature Trend of Hot Strip Rolling Material. It is not material for sectional beams. The temperature s trend is almost same in both hot strip and sectional beams. The surface cools faster than the center of the material. Though the surface temperature drops due to conduction by Roll and by convection by cooling water at each rolling mill stands, surface temperature Figure 9.8 Temperature of rolled material *2) revives due to conduction inside the material by heat inside the material. After some idling time, surface and center of the material are simultaneously cooled to similar temperature. The accuracy of the material temperature is critical to Deformation Resistance Estimation, which is most important to the Rolling Pass Schedule calculation. Deformation resistance In the calculation of Rolling Force P, it is necessary to know accurately Deformation Resistance Km. Figure 9.9 shows two samples of Measured Deformation Resistance of Carbon Steel in hot state. Deformation Resistance depends not only upon the kind of material, but also on strain, strain rate and deformed temperature. Furthermore it is affected by History of Rolling. In order to calculate rolling force, it is necessary to obtain Deformation Resistance, for various material grades under various conditions. Calculated result is necessary to be compiled easily to be commonly used for various applications. Where e is Logarithmic strain which is shown as following equation; e= 2 h0 log ( 3 h ) (9.6) Where h 0 is initial thickness at the exit of roll gap And Figure 9.11 shows Temperature Dependence to Deformation Resistance of Carbon Steel 90

93 Figure 9.9 Deformation resistance of Carbon Steel *2 Figure 9.10 Deformation Resistance vs. Temperature & Strain Rate *2 The Deformation Resistance is proportional to the Logarithm of Strain Rate and it is roughly inverse proportional to temperature. In detail Deformation Resistance changes not uniformly in accordance with temperature due to metallurgical transformation. Generally since Compressive Strain amount in roll gap gradually changes from entrance to exit of the roll gap, Averaged Deformation Resistance is used for simple calculation of Rolling Force, except special numerical calculation. Averaged Deformation Resistance is obtained by Integration of Deformation Resistance in accordance with progress of rolling from the entrance to exit of roll gap. K 0m = 1 ε ε 2 1 e2 k 0 ds (9.7) e1 Figure 9.10 shows Strain Rate dependence to Deformation Resistance of Carbon Steel Where e 1 and e 2 are Strain in the rolled material, e 1 is Strain at the entry; e 2 is Strain at the exit of roll gap. Though if the initial strain is 0 then e 1 =0, if the initial strain is not 0, which is residual strain of preceding rolling pass, the integration is calculated with e 1 of not 0. Averaged Deformation 91

94 Resistance is calculated by integration between e 1 and e 2. The difference of strain e 2 -e 1 shows the cumulative amount of strain which is generated during the rolling pass. Though in case of some cold rolling, the initial strain e1 is not 0, in general case of hot rolling the initial strain is 0 because in hot rolling pass, strain in the preceding passes does not remain due to re-crystallizing and recovery of grain structure are carried out. It means that Averaged Deformation Resistance is obtained by the following equation: K 0m = e2 1 ε k 0. ds (9.8) 2 e1 Throughout the Rolling Process the Deformation Resistance needs to be small enough for that the Rolling pass schedule can be successfully completed. 9.4 Rolling Force and Rolling Torque (Moment) Theory of Rolling Rolling mills in Bhavnagar district manufacture sectional products. Here except very little rolling mills, the sectional products are rolled not with Universal Mill but with grooved roll, which is called Caliber Roll. In the sectional rolling, metal flows not only two dimensionally to the downstream direction but also three dimensionally to the transverse direction of rolling. Actually, however in the sectional product rolling process, for simplification of theory, the rolling process is simplified to two dimensional flat rolling. Figure 9.12 and Figure 9.13 show the Fundamental Images of Stress Balance in Flat Rolling. Figure 9.12 Basic image of Flat rolling *2 By the compressive force which is given by both rolls, in the rolled material the compressive force in radial, tangential and transverse directions are generated. When the rolled material is longitudinally pulled from both sides, the tensile force helps the rolled material deform by plastic deformation. Without such longitudinal tensile force however, the rolled material needs more compressive force to deform. In the rolling process, thickness is decreased in accordance with progress of the rolling process. It is called Reduction. On the other hand, material speed increases inversely proportional to thickness change. In the rolled material multiplication of thickness and speed is constantly maintained from the entry to the exit of the roll gap. H 1 * v 1 = h n * v n = h 2 * v 2 (9.9) Where, H: Entry thickness, h: Exit thickness, v: Speed around roll surface, 1: Entry, 2: Exit, n: Neutral point In the upstream area of the neutral point, the rolled material goes slower than roll surface, on the contrary in the downstream area than the neutral point; the rolled material goes faster than roll surface. Neutral point means the point where the rolled material moves simultaneously with roll surface. Figure 9.13 Force balance in Rolling *2 Rolling Force P and Rolling Torque G are fundamental parameters to determine Rolling Pass Schedule and Roll Gap Setting. Rolling Force is obtained by integration 92

95 of vertical (Compressive stress) around roll surface from the entry to the exit of roll gap, and Rolling Torque is Momentum around Roll Center. P= b*k m *Q r * ( R'*( H h) (9.10) G= P*a (9.11) Where a: Torque Arm Length (mm) Rolling power is shown by the following equation; L= A v *G* y R (9.12) Where A: Power transformation Factor, y: Mechanical efficiency of the Rolling Mill, v: Rolling Speed (radian/s), R: Radius of Roll Such parameters as Rolling Force, Rolling Torque and Rolling Power are compared with specification of the rolling mill. If every parameter does not exceed specified value for the rolling mill, the rolling pass is available. But if any parameter exceeds the specified value, the rolling pass is not available. For such rolling pass, reduction ratio should be decreased, and calculations should be done again. Rolling Speed means angular speed at the neutral point in the roll gap. If roll radius is R, longitudinal speed V is V= v * R 2*π (mm/s) (9.13) The Rolling Speed affects not only directly to Rolling Power, but also to Rolling Force and Rolling Torque, due to stress balance in the roll gap. If material length is given, rolling time is inversely proportional to the longitudinal speed V. If the Rolling Speed is too high, machines such as Roll, Driving Shaft, Screw down Mechanism Roll driving Motor will be broken by over load. On the contrary, if the Rolling Speed is too low, the Rolling Time becomes too long. It causes cooling down of rolled Material. If the material temperature becomes too low, the Deformation Resistance becomes too high. It causes difficulty of rolling pas, due to excess of Rolling Force, Rolling Torque and Rolling Power. Many researchers such as Siebel, Karman, Orowan, Nadai, Hill, Sims and so on studied theoretically, and solved differential equations with specified assumptions, to obtain simplified models for actual rolling work. 9.5 Rolling Pass Schedule and Temperature Prediction during Rolling Figure 9.14 shows the outlined concept of rolling pass schedule. In order to obtain rolled product with good dimensional accuracy and good surface quality within good energy efficiency and within such mechanical limits of rolling mill specification as Rolling Force, Rolling Torque and Rolling Power, such rolling pass schedule as Figure 9.14 is necessary. 93

96 Figure 9.14 Outlined Concept of Rolling Pass Schedule Although the necessary condition depends upon kind of product in detail, the Outlines of Rolling Pass Schedule are almost similar to the following: q Prepare the data of the initial material temperature, the initial dimensions of rolled material, the final dimensions of aimed product, the mechanical properties of the rolled material and mechanical limit values specified to the rolling mill. q Assume the maximum reduction, and calculate the estimated material thickness and length at 94

97 q q q q the exit of roll gap. Simultaneously such mechanical limits as Rolling Force, Rolling Torque and Rolling Power are checked by applying Deformation Resistance in accordance with material temperature. If any mechanical specification exceeds the limit value, decrease the reduction and calculate again similar to the step (2). If no mechanical specification exceeds the limit value, carry out the rolling in accordance with the assumed reduction. Estimate average temperature at the finishing time of the rolling pass. And based upon the estimated material temperature, search the Deformation Resistance of the material at the finishing time of the rolling pass by referring to some Deformation Characteristics. Repeat the calculating procedures from the step (2) to the step (5) until the exit thickness becomes thinner than the aimed thickness at the exit of the roll gap. 9.6 Rolling of Sectional Products and Tandem Rolling Figure 9.15 shows Metal Flow of the Rolled Material by three kinds of Caliber Roll for Cross Sectional product rolling. Sectional Products are made by using so called Caliber Roll which is grooved on the surface of roll drum in accordance with rolling process. Since in Caliber Rolling compared to Flat Rolling, the behavior of material in the roll gap is more complex, generally it is very difficult to treat theoretically starting from fundamental equation of plastic dynamics similar to flat rolling. The fundamental rolling characteristics are Rolling Force, Rolling Torque, Wide-spreading and Advancing. The Rectangular Transformation Method was applied as a simplifying method, which replaces appropriate rectangular sectional material from Caliber Rolling to Flat Rolling. Though this method can utilize proven knowledge of Flat Rolling, since some conditions specific to Caliber Rolling are neglected, accuracy of Rectangular Transforming Method was insufficient. Recently for each typical Caliber Rolling, deforming behavior, pressure profile etc. have been experimentally solved, relatively simple process and easy to make numerical model has been made clear. In accordance with such advance, direct and accurate methods to calculate fundamental characteristics have been developed. Figure 9.15 Metal flow pattern by Caliber Rolling *2 Caliber Rolling has the following features:. q Non-uniform distribution of Reduction Ratio in transverse direction q Non-uniform distribution of Projected Length of Contacting Arc q Constraint of Material flow in transverse direction by Caliber Roll side wall q Profile and Discrepancy of Roll Radius and Surrounding Speed between Upper and Bottom q Temperature Profile in the Rolled Material In Caliber Rolling, in accordance with Caliber shape, Upper and Bottom Rolls have different Radius in transverse direction, and Roll Radius at same position may be different between upper and bottom rolls. Since in flat rolling, rolled material mostly flows out to the longitudinal direction, no friction happens in the transverse direction. On the hand in the caliber rolling, since the rolled material flows not only to the longitudinal direction, but to transverse direction, friction between roll surface and the material happens because of surrounding speed difference. Due to such friction Rolling Torque of 95

98 Caliber Rolling becomes larger than Flat Rolling. Figure 9.16 Rolling Force Profile according to Contacting Arc angle *2 The cross sectional temperature profile in the Rolled Material by Caliber Rolling becomes more complex in accordance with complexity of caliber form. The temperature profile increases complexity of Deformation Resistance profile in the cross section of the rolled material. It causes estimation error of Deformation Resistance all over the rolled material cross section. Figure 9.16 shows a Contacting Arc Profile and Rolling Force Profile, those are related to the rolling of square shaped material with oval shaped caliber roll. Though at the width center the rolling force is almost uniform all over the contacting arc, near the width end the rolling force is higher in average than the force at the center, and it remarkably varies along the contacting arc. Especially the Rolling Force profile has a sharp peak near the entrance of the contacting arc. Tandem Rolling Rolling process with plural rolling mills more than one rolling mill is called Tandem Rolling, in which rolling process one rolled material is rolled with pinching and pulling by adjacent two rolling mills. Though the Tension in the Rolled Material by two rolling mills is effective to decrease Rolling Force, it is difficult to accurately control the Tension within the allowable limit of the material. Too strong tension causes not only too small product s cross sectional area, but in the worst case the material may be broken. Too weak tension causes not only too large product s cross sectional area, but in the worst case the rolling mill may be broken. Figure 9.17 shows the Affect of Front and Back Tension to the Rolling Force. The Rolling Force Ratio is almost proportional to the tension in the Rolled material. And the more cross section changes, the larger Rolling Force Ratio becomes. 9.7 Lubrication and Water Cooling for Roll Roll Surface is heated by hot Rolled Material as well as generated heat by friction between Roll Surface and Rolled Material. Especially when sectional product is rolled, friction between Roll Surface and Rolled Material becomes more significant than the friction in Flat Rolling. After some rolling time, Roll Surface becomes rough and too hot, and it causes surface defect of product, as well as roll breaking trouble. In order to prevent such problems it is useful to cool roll. In case of cooling of roll, it is important to maintain the water seal around roll neck to prevent lack of lubrication of roll neck bearing. If water enters into lubricated bearing at the roll neck, since lubricant (oil or grease) cannot maintain ability of lubrication, it may cause mechanical damage of such bearing. Figure 9.17 Back tension vs. Rolling force *2 Sometimes Roll is cooled and lubricated with emulsion of oil and water, which has better affect for Roll surface as well as electric power 96

99 saving for rolling work than with just water, it however costs waste water treatment to prevent water pollution. Cooling water (Coolant) is usually recycled and re-used by removing scale (Oxidized iron powder) and oil (or grease) in order to save water resource, as well as to prevent water pollution. 9.8 Roll Grinding to Revive Roll Surface Although Rolls for rolling process need to have Heat Crack Resistance, Wear Resistance and Toughness, it is difficult to have all of them together by one kind of material. It is necessary to select Roll Material appropriate to use. As the Roll Material, Cast Steel, Forged Steel or Cast Iron is used. Cast Steel was widely used because of the mechanical property that has low hardness but good strength by addition of some alloy components, large dimension of roll is available, and it is suitable for mass production by use of casting mould. Recently Forged Steel has increased to be used for roll, because of better mechanical properties, especially better toughness. By supplanting Cast Steel to Forged Steel Roll, Roll neck break has decreased. Since Cast Iron is less expensive, higher hardness and more easily manufactured, it was used more than Cast Steel Roll and Forged Steel Roll in the old time. But in recent years it has been supplanted by Cast Steel and Forged Steel because of mechanical brittleness. Furthermore since it is very difficult to obtain many mechanical properties together by single material, it has increased to compose the roll by Complex Casting Method and Sleeve Interdigitation Method. In Complex Casting Method, as the inner layer tough material, and as the outer layer, wear resistant, heat crack resistant and spalling resistant material are centrifugally cast to be metallurgically connected. In Sleeve Interdigitation Method, the inner body made of tough material, and the outer sleeve made of wear resistant, heat crack resistant and spalling resistant material is interdigitated and mechanically connected. Since Wear and Roughness of Roll surface affects the product surface quality, in order to maintain good product surface quality, Roll Surface needs to be ground in accordance with rolling time or amount of rolled product. Although generally the depth of roll grinding is 0.6mm to 1.0 mm for Wear and Roughness of Roll surface, in case of heat crack and degrading of roll hardness. Dimension difference between upper and bottom rolls should be within the control limit to prevent warp of the rolled material. In case of Caliber Roll, groove is formed by grinding over the roll body. Groove of the Caliber Roll is more worn than flat roll due to friction between roll surface and rolled material. In the roll maintenance shop the following works are carried out. q Roll grinding and Roll dimension maintenance q Disassembling assembling and cleaning of roll bearing q Management of Bearing, Bearing case and Liners 9.9 Automated Rolling Mill Control System Generally automation of rolling process is composed of Automatic Dimension Control and Automatic Mechanical Properties Control, which includes Automatic Material Transfer Control. Automatic Dimension Control means to control such cross sectional dimension as Thickness, Width and Height. Generally total length of the product is obtained as the controlled result of such cross sectional dimension. In order to control such cross sectional dimension, fundamentally product dimension, rolling force and roll gap are measured and fed back to adjust roll gap. 97

100 Diameter of the round product and height and width of H shaped product are measured based on opto-electronic method. Thickness of Web and Flange of H shaped Product are measured by Radio isotope. Such measured value is fed back to the dimension controller and compared with aimed dimension to adjust roll gap. Rolling force is measured with so called Load Cell. Rolling force is used to automatically compensate the actual Rolling gap which changes in accordance with rolling force. Especially when the deformation resistance is changed in accordance with material temperature, even if entrance dimension is same, exit dimension is changed due to fluctuation of rolling mill stand stretch by the fluctuation of rolling force. Roll gap is measured by angular position sensor for the electric screw down motor, or piston position sensor for the hydraulic cylinder. Automatic Mechanical Properties Control means to control Mechanical Properties like Strength, Toughness, Elongation (Ductility) and Hardness. Mechanical Properties are controlled based upon numerical control model which is experimentally made mainly by Metallurgical components of the rolled material and thermal history. The thermal history means Trend of Temperature change which includes Heating Rate and Cooling Rate. In case of Controlled Rolling, in addition to the thermal trend above, Rolling Ratio at certain Temperature is necessary to be kept. In order to obtain the numerical control model of mechanical properties, in accordance with chemical component, rolling pass schedule with trend of material temperature is determined, and as the result of manufacturing, mechanical properties are tested. In order to measure the material temperature, Infra-red Radiation Pyrometer is used. Recently not only average temperature in the transverse direction, but also temperature profile in the transverse direction is measured with temperature profile meter Facilities Maintenance for Stable Operation Figure 9.18 and Figure 9.19 show the fundamental concept of facilities maintenance especially for continuous manufacturing process. In each process row, the material is changed to the product in the process, and the residual part of material becomes Fall out or Scrap. If scrap is fallen out, the raw material and energy that was consumed up to that process becomes lost. Especially in such continuous process as Figure 9.19, the scrap which is generated at Machine4, material of Machine4 contains integrated energy from Machine1 to Machnie3. So scrap of Machine4 includes not only energy which is consumed in Machine4, but also integrated energy from machine1 to machine4. If rolling mill stops operation due to unexpected trouble such as mechanical breakdown, it affects not only the material in the rolling mill but also the material in upper stage of the rolling mill like re-heating furnace, because the material which has already been heated enough for rolling cannot be discharged. In such a case the material in the re-heating furnace becomes over heated. It causes not only lot of scale generation and energy consumption, but also in some cases the whole material may become scrap. So it is important for good product quality, little energy consumption, high product yield, preventing pollution to maintain the facilities under stable condition. In order to maintain the facilities under stable condition, it is necessary to execute various maintenance activities. In the rolling mill the most significant maintenance for product quality is roll exchange and roll grinding. Except unexpected break down the timing of roll exchange can be predicted by the amount of rolled material. Other than Roll Exchanging, Lubrication of Bearing, Exchange of Bushing (slipping type bearing), Exchanging of Seal Packing for roll neck bearing, Cleaning or Exchanging of Filter for hydraulic system and Exchange of slipper metal of universal joint between driving motor 98

101 Figure 9.18 Concept of Manufacturing Process Figure 9.19 Concept of Continuous Process and roll neck are necessary to be carried out. Some of maintenance activities are enough to be done periodically. Some other maintenance activities need to be done as per requirement. For example in case of Seal Packing for roll neck bearing, entering of water into bearing case can be known by milky colored emulsion of grease. Gap between slipper metal and roll neck is known by measuring clearance between both slipper metals in the coupling with extracting roll during the maintenance time. Since the concept of facilities maintenance is common between rolling and reheating furnace, Figure 9.18 and Figure 9.19 are useful in the study. 99

102 9.11 Reference List Name of Book Publisher Editor Year Eutectic in free encyclopedia Wikipedia ja.wikipedia. org/ 10 Iron & Steel Handbook The 3id Edition, III Maruzen ISIJ 80 (1) Base of Rolling, Plate & Strip New Edition Industrial Furnace Handbook ECCJ Japan Industrial Furnace 97 Association Textbook for The 4th Special Lecture on ECCJ ECCJ 07 Thermal Field Handbook on Energy Conservation Audit Technologies (for Factory) ECCJ ECCJ 07 The 5th Edition Lecture on Heat Management Technologies Maruzen Central Heat Management 72 Association (Japan) [Note] ISIJ: The Iron and Steel Institute of Japan ECCJ: Energy Conservation Center, Japan Mr Kioyshi Hitomi, a Rolling Mill Expert from Japan has contributed with literature and general suggestions from his expertise in framing up this piece of article with help of Mr Sakae Tezuka. He has also made suggestions in taking measures in improvization of rolling mill operation of the Bhavnagar rolling mill industries and has been greatly appreciated by the stakeholders. Mr Kiyoshi Hitomi Expert of Steel Rolling 100

103 Chapter 10: Fundamental Technologies on Reheating Furnace for Steel Rolling 10.1 Necessary Conditions for Reheating Furnace in Steel Rolling Mill Necessary conditions and countermeasures to realize the necessary conditions for steel rolling mill are summarized in Table Mr Sakae Tezuka Table 10.1 Necessary Conditions for Steel Re-Heating Furnace Product quality Item Necessary Condition Countermeasures to Realize Necessary Condition 1) Mechanical properties and metallurgical properties which are uniform and appropriate to aimed values 2) Uniform shape and dimensional accuracy which is within aimed accuracy 3) Good surface quality 1) Appropriate heat pattern with appropriate discharging temperature 2) Accurate mathematic control model for heating 3) Good maintenance for re-heating furnace and transportation facilities Productivity Primary product yield Energy efficiency Environmental Effect Safety Heating rate appropriate to sales order with least human power Maximum yield with least fallen-out scrap and scale loss Least energy consumption for good quality, appropriate productivity, good environment and safety Least pollution without vibration nor noisy sound Least danger of firing, explosion and pinching Automatic control with measuring instruments and computer system Accurate discharging temperature under stable operation Good furnace, good heat pattern, good rolling pass schedule and stable rolling operation Good combustion Good facilities maintenance The most significant parameter for energy efficiency is material heating temperature. The material temperature needs to be measured and estimated as accurately as possible. In order to measure the material temperature in the furnace during heating, usually thermocouple sensor is used. When the thermocouple is installed, the sensor needs to be located as close to the material surface as possible, without disturbance. The characteristics of the ambient gas affects surface properties of the product. In order to control ambient gas characteristics, Oxygen concentration in the combustion gas is most significant. Too low Oxygen concentration causes incomplete combustion of fuel, and incomplete combustion causes energy loss, black smoke generation and difficulty of scale removal from surface of the heated material. On the contrary too high Oxygen concentration causes much amount of waste gas and much generation of scale on the surface of the heated material. 101

104 10.2 Heat Balance and Thermal Efficiency Heating temperature is the most significant parameter to consider the energy efficiency of the reheating furnace. In order to determine the heating temperature, kind of material (steel grade), material dimension, product dimension, capacity of the rolling mill, and energy price etc are considered. As described in 9.3, throughout the rolling process the deformation resistance needs to be small enough to complete the rolling. So the discharging temperature needs to be high enough even after cooling down at the end of the rolling process because the Deformation Resistance depends upon the material temperature, discharging temperature. However it should not be too high because that will prevent scale generation. It means that the discharging temperature from the re-heating furnace should be between the upper limit and the lower limit. In order to obtain the discharging temperature appropriate to complete rolling, it is necessary to heat in accordance with specification of the material. In the re-heating furnace, the material is heated with burner. The major heat transfers in the re-heating furnace without recuperator are as follows: q Radiation from combustion flame and combustion gas q Radiation from furnace wall and furnace ceiling q Convection from combustion flame and combustion gas q Cooling by conduction to skid q Heat generated by combustion of fuel q Waste gas heat at the exit of the furnace q Radiation and convection heat from outer surface of the furnace q Conduction from skid to the floor of the furnace In case recuperator is used to recover the waste gas heat for preheating combustion air, the following is added as coming in heat. q Pre-heated air heat In such a case (6) needs to be revised as follow, (6) Waste gas heat at the exit of the recuperator Aimed value of discharged material temperature appropriate to successfully complete rolling is determined by consideration in After being charged into the furnace the charged material is heated by combustion gas, hot furnace wall and hot furnace ceiling. Hereinafter Furnace Wall and Furnace Ceiling is refered as Furnace Wall in total. Theoretically heat transfer among combustion gas, furnace wall and heated material are analyzed with Radiation, Convection and Conduction. Define the following nomenclatures. A: Theoretical combustion air amount C: Specific heat (kj/m3 o C) F: Surface area (m 2 ) G: Combustion gas amount (m 3 /h) Q: Heating rate (kj/h) 102

105 q: Heating value (kj/kg) T: Absolute temperature ( K) l: Length (m) m: Air ratio (Air excess factor) t: Celsius temperature ( C) W: Flow rate (kg/s etc.) Φ CG: General heat transfer coefficient or general heat Absorption coefficient a: Heat transfer coefficient (kj/m2h C) by convection g: Specific weight (kg/m3) e: Emissivity h: Efficiency q: Time (h) l: Thermal conductivity (kj/mh C) by conduction s: Stefan Boltzmann s Constant Subscript a: Actual Subscript h: High Subscript l: Low Subscript d: Conduction Subscript f: Fuel Subscript g: Combustion Gas Subscript m: Heated Material Subscript r: Radiation Subscript t: Theoretical Subscript v: Convection Subscript w: Furnace wall or Furnace ceiling Subscript w g : Waste Gas Heat generated by combustion of fuel is described as follow. Q f = W f * q f (kj/h) (10.1) When there is one solid body in the space relatively much larger than the solid body with surface area F, heat is transferred by Radiation. Heat transfer with Radiationis shown by the followings. Q r = 20.43e *{(T h /100) 4 -(Tl/100) 4 }*F (kj/h) (10.2) Figure 10.1 shows how heat flows by radiation in the furnace. Figure 10.1 Heat traveller by radiation *2 103

106 Heat transfer with Convectionis shown by the following: Qv=a *(t h -t l )*F (kj/h) (10.3) Heat Transfer Coefficient a depends upon the followings. (1) Kind of fluid (2) Direction of Flow: Horizontal, Vertical etc. (3) The state of flow, so called Laminar Flow or Turbulent Flow. Especially in Turbulent Flow, the coefficient depends upon Reynolds Number Re and Prantle Number Pr. (4) Kind of Convection: Natural Convection or Forced Convection Figure 10.2 shows Heat Transfer by Convection *3 Figure 10.2 Heat transfer by convection *2 Combustion gas around the heated material usually flows in turbulent convection, and ambient air around the furnace body flows in natural convection. Figure 10.3 shows heat transfer by conduction. In case of one wall isolates two spaces and the temperature of both sides are th and tl, Heat transfer with Conductionis shown by the following. Q d = l λ (th -t h )*F (kj/h) (10.4) Heat transfer from the surface to the depth of the heated material is similar to the conduction through the single layered wall. Heat which reaches from combustion gas (including combustion flame) to inside of furnace wall (including furnace ceiling) is insulated by such thermal insulator as brick and glass fiber, in order to prevent Figure 10.3 Heat transfer by conduction *2 the heat to dissipate from outside of the furnace wall. Even if thermal insulator is used at furnace wall and roof, the penetrating heat can not be completely prevented, but some part of heat still penetrates through the insulator. In case of three layered wall in series isolates two spaces with temperature th and tl, Heat transfer with Conduction is shown by the following. Q d = 1 R (t -t h l 0 )*F (kj/h) (10.5) l l l Where Total Thermal Resistance R 0 = λ 1 + λ 2 + λ 3 (10.6) Though elemental equations of each heat transfer phenomena are as shown above, in actuality transferred heat to the material in actual furnace is shown by the following equation. T h Q cg =20.43* Φ CG *F*{( 100 T l )4-( 100 )4} + a*f*(th -t l ) (10.7) Where Φ CG is called General Heat Transfer Coefficient or General Heat Absorption Coefficient, which summarizes radiation heat transfer from such various points as combustion flame, combustion gas and furnace wall. 104

107 In the real re-heating furnace, temperatures become as follows. T h =T g (10.8) T l =T m (10.9) They mean that heat source with higher temperature Th is weighted average of combustion gas (including combustion flame) and hot furnace wall, and heat sink with lower temperature is heated material. In the heated material, heat transfers from hot surface into cold depth by conduction heat transfer. Actual amount of combustion gas per unit flow rate of fuel is as follows: G a = G t +(m-1)*a (10.10) Since actual flow rate of fuel is Wf, Actual amount of combustion gas per unit time is as follows: W ga = W f,*g a (10.11) After heating the material the combustion gas flows out from the furnace with temperature of t go. The waste heat loss is as follows: H wg = W ga *C g *( t go. -t 0 ) (10.12) In order to estimate the efficiency in a plant, it is useful to make Mass Balance and Energy Balance. Especially in the thermal process, it is useful to make Heat Balance, which shows a balance sheet of incoming heat and outgoing heat. Major parts of incoming heat are as follows: (I1) Visible heat of Material brought into furnace (I2) Heat generated by combustion of fuel (I3) Heat of pre-heated combustion air (in case of recuperator is used) (I4) Phase Transformation Heat of heated material Major parts of outgoing heat are as follows: (O1) Visible heat of material brought out from furnace (effective heat) (O2) Heat brought out by waste gas at the entry of the recuperator (in case recuperator is used) (O3) Heat penetrating through and dissipating from furnace wall (including furnace roof) (O4) Heat dissipating through opening of furnace body (O5) Heat cooled by entraining air (O6) Heat dissipating through skid pipe to furnace hearth Figure 10.4 shows the effect of charging temperature to Specific Energy Consumption, and Figure 10.5 shows the effect of discharging temperature to Specific Energy Consumption. In order to improve specific energy consumption, it is effective to raise charging temperature and to lower discharging temperature. 105

108 Figure 10.4 Charged temperature vs. Improvement of Specific heat consumption *2 Figure 10.5 Discharged temperature vs. Specific energy consumption *2 In order to raise charging temperature, Hot charging or Direct rolling are applied. Both of them are rolling processes after continuous casting process. The former is charging material into re-heating furnace before cooling down, and the latter is directly sending material to rolling mill without reheating in the re-heating furnace. In order to lower the discharging temperature, it is necessary to determine the lowest discharging temperature necessary ad enough for rolling. This concept has already been described in Table Figure 10.6 shows the effect of Input heat to some parameters regarding furnace performance. Input heat amount has the best value for furnace performance. Figure 10.7 shows the heat flow diagram of re-heating furnace of which heat balances are shown in Table 10.2 and Table The heat flow diagram graphically shows the state of heat flow in the Whole furnace including both of the main furnace and recuperator each. Figure 10.6 Input Heat vs. Furnace performance *2 Figure 10.7 Heat Balance Diagram of WB furnace *3 106

109 Table 10.2 Heat Balance Tables of Whole Furnace *2 Incoming Heat Outgoing Heat Item Heat (MJ/t) % Item Heat (MJ/t) % Combustion Heat of Fuel Visible heat of discharged material Visible heat of combustion air 0 0 Visible heat of discharged scale Scale generation heat Visible heat of waste gas Cooling water loss Dissipated heat from furnace body Total Total Table 10.3 Heat Balance Tables of Main Furnace *2 Incoming Heat Outgoing Heat Item Heat (MJ/t) % Item Heat (MJ/t) % Combustion heat of fuel Visible heat of discharged material Visible heat of combustion air Visible heat of discharged scale Scale generation heat Visible heat of waste gas Cooling water loss Dissipated heat from furnace body Total Total Table 10.4 Heat Balance Tables of Recuperator *2 Incoming Heat Outgoing Heat Item Heat (MJ/t) % Item Heat (MJ/t) % Visible heat of combustion air at recuperator entrance 0 0 Visible heat of combustion air at recuperator exit Visible heat of waste gas at the entrance Visible heat of waste gas at recuperator exit Dissipated heat from recuperator Total Total

110 10.3 Material surface defect due to oxidation and scale Generation Surface defect due to scale generation and scale removing Regarding re-heating furnace, it is significant to design and to operate the furnace not only in order to decrease energy consumption but also decrease surface defect due to scale on the surface of the rolled material. Table 10.5 shows countermeasures to decrease scale generation on the surface of steel material in re-heating furnace. Table 10.5 Countermeasures to decrease Scale Generation Rough Countermeasure Detail Countermeasure 1. Reducing scale generation 2. Smooth scale removing Shortening heating time duration Heating temperature Lower air ratio to decrease Oxygen in combustion gas Prevent entrain air out of furnace Scale preventing paint (in some cases) Mechanical scale breaker Hydraulic de-scaling device 10.4 Heating Capacity of Furnace appropriate to Rolling Mill s Productivity Balance of heating capacity of furnace vs. rolling capacity of rolling mill is very significant. When the heating capacity of furnace is too large compared to rolling capacity, the heated material is frequently over heated, and since combustion is stopped in order to prevent over heating, energy consumption will become more than the furnace with appropriate heating capacity. When heating capacity of furnace is too small compared to rolling capacity of rolling mill, since the heated material is not heated enough to roll, the rolling mill can roll the material less than the specified capacity of the rolling mill, because of rolling force limit or rolling torque limit. If the rolling mill rolls the material which is not heated enough, rolling machine may be broken by over load due to large deformation resistance of the material because of too low material temperature. On the other hand within the furnace, balance of burner and the furnace body is necessary to be considered. Figure 10.8 Economical Hearth Capacity *3 Figure 10.8 shows an example of Economical Areal Cover Ratio. Areal Cover Ratio means Heating Capacity of Burner in unit furnace hearth area. On the other hand Heating Capacity of Burner in unit furnace volume is called as Volumetric Heating Capacity, When Areal Cover Ratio or Volumetric Heating Capacity is too large, in other word, too much fuel is supplied to the burner relatively to unit furnace floor area or to unit furnace volume, furnace cannot completely heat material in the floor area or in the furnace volume. In such a 108

111 case, the fuel which is supplied to the burner cannot be completely burnt, but the incompletely burnt flame flows out through the furnace exit. It causes high temperature of waste gas and much exhaust of incompletely burnt emission. It induces low furnace efficiency and bad environmental effect. Figure 10.9 shows the effect of furnace length expansion to decrease specific energy consumption. Though longer furnace has advantage of lower exhaust gas temperature, because the exhaust gas heats the material enough in the furnace, in such longer furnace, dissipation heat loss from the furnace surface may increase. In addition, in such longer furnace, in case of water cooled furnace, cooling water heat loss may increase. So furnace length is limited to certain range. Figure 10.9 Furnace length expansion vs. Specific fuel consumption * Heated Material (Kind & Dimension) Regarding metallurgical view point, heated material is determined by the concept which is based upon thermo-mechanical properties of product, which is made with the material. Shape and Dimension of the heated material is determined according to the product, the material can be easily heated and can be effectively rolled. Generally such flat products as plate and sheet are made from such rectangular material as slab. Such thin and long products as bar, beam and wire are made from ingot or billet. For the special product, H shaped sectional beam is made from slab or beam-blank. In some countries such as India, ship break scrap is used as rolled material. Since the ship break scrap has various shapes and dimensions, it is difficult to uniformly heat and to accurately roll Zoning and Heat Pattern in the Furnace In order to carry out energy conservation in re-heating furnace, it is very important to consider the following. One is zoning and capacity profile of each zone, the other is temperature profile in each zone, which is called Heat Pattern.Figure shows an example of Pusher type Furnace with three zones. In order to uniformly heat both sides of the material, not only upper burners but also bottom burners are installed. In order to precisely control heating the material, furnace was divided and number of zone was increased. Figure shows an example of Pusher type Furnace with Figure Pusher furnace with three zones *3 five zones. In such furnace with many zones furnace temperature can be accurately controlled individually in each zone. Though the material needs to be heated continuously in the furnace enough for rolling, if the heat supplied to the burners are too much, not only the material is over heated and material surface is oxidized to generate scale, but most of thermal energy supplied to the furnace is also lost. Especially in case of short furnace with much Figure Pusher furnace with five zones *3 109

112 Figure Comparison of Heat pattern heating load at pre-heating zone, the material inside is not heated enough by conduction from the surface of the material, but only the surface of the material is heated by radiation and convection from combustion gas and furnace wall during its travel in the furnace. In such a case exhaust gas temperature is too high to generate much exhaust gas heat loss. In the long furnace with much heating load at heating zone, since the heat supplied through burner is slowly and fully given to the material, exhaust gas temperature becomes low. It means that in such a long furnace waste gas heat loss becomes little, and the furnace has high energy efficiency. In addition, not only the total heat supplied throughout the furnace, but also heat pattern in the furnace affects the product quality, thermal efficiency of the furnace and electric power of rolling mill motor. Figure shows comparison of heat patterns of the furnace with three zones, which are upper pre-heating zone, bottom pre-heating zone and upper heating zone. Figure 10.12, is an example of heat pattern of a short furnace with only upper burners in two zones. In order to obtain the total heating capacity in a short furnace enough for the rolling operation, the heating capacity of the burner in the pre-heating zones needs to be large. In addition in this furnace, since burners are installed only at the upper side of the material, bottom side of the material is not heated but only upper side of the material is heated by combustion flame, combustion gas and furnace wall. Such burner location causes single side heating of the material. Though theoretically heat transfer by radiation to the surface of the material takes place in a short time, it takes long time to transfer heat by conduction inside the material. When thick material is heated, if burner at only upper side is burnt, bottom side of the material is not heated but only upper surface is heated. In such a case, temperature on the bottom surface does not increase so much, but the temperature only at the upper surface becomes high. If both side burners are simultaneously burnt, not only upper surface but also bottom surface of the material is simultaneously heated. In such a case it takes about a half of the heat transfer time of the furnace with single side heating, from the hottest point (material surface) to the coldest point (material thickness center). On the other hand, in case of single side heating, for example, only upper side burner is used, the hottest point is upper surface, and the coldest point is bottom surface. In such a case as single side heating, the thickness through which heat transfers is equilibrium about double of the heat transfer thickness in case of double side heating. 110

113 The energy efficiency in one furnace can change according to the amount of heating load. When the material is rapidly heated with high heating load, which is called Full Load Operation Mode, more heat is supplied to the furnace, and waste gas heat loss and dissipation heat loss become larger than the heat loss of slow heating with lower heating load, which is called Energy Saving Mode. Heat Pattern means the profile of ambient temperature in the furnace. In accordance with heat pattern, sometimes heated material can not be heated enough for rolling. And in the other case, the heated material is heated too much to generate scale. In both of these cases there will be energy loss. So heat pattern needs to be determined based upon furnace structure and furnace characteristics, and in order to improve thermal efficiency, the heat pattern needs to be based upon the following concept: (1) In thin material, since heat transfer time from the surface to thickness center is short, furnace temperature set values of pre-heating zone and heating zone should be low. In some cases combustion in pre-heating zone is stopped and waste heat of combustion gas from heating zone heats the material in pre-heating zone. (2) In thick material, since heat transfer time from the surface to thickness center is long, furnace temperature set values of pre-heating zone and heating zone should be high in order to heat the material enough. In this case though the material can be heated enough, exhaust gas heat loss may become much and thermal efficiency may become low, because the waste gas temperature becomes high at the exit of the furnace. In addition the surface of the material may be over heated and scale may be generated Fuel As fuel to burn in the re-heating furnace, gaseous fuel, liquid fuel and solid fuel are used individually or synchronously in parallel. Gaseous fuel and liquid fuel are usually easier to control the flow rate but more explosive than solid fuel. In case of pulverized coal is used, the pulverized coal is similar to gaseous fuel or liquid fuel regarding controllability and explosiveness.in case of air is used to transport the pulverized coal, air may be supplied excess to theoretical amount enough for complete combustion. In case fuel is burnt to heat material in re-heating furnace, it is necessary to consider the following: (1) Heating Value: There are two kinds of Heating Value, Higher Heating Value with latent heat for condensation of water in the combustion gas, and Lower Heating Value without latent heat for condensation of water in the combustion gas. Usually in case of heat balance calculation Lower Heating Value is used, because the latent heat can not be used, when the combustion gas temperature is higher than evaporation temperature. When gaseous fuel is used with flow rate measurement by differential pressure which is measured by orifice or Pitot Tube, so called Wobbe Index is used to consider and design burner capacity. H Wobbe Index W= ρ where H is Heating Value, ρ is Specific Weight. (10.13) (2) Ignition Temperature (or Ignition Energy): When fuel begins to burn, there must be Oxygen (or Air) and energy to ignite (or temperature to begin combustion). Ignition temperature is the lowest temperature to begin combustion without any other heat, and it depends upon measuring method, air ratio, pressure and flowing speed. Generally ignition temperature in Oxygen is about 20~50 o C lower than in air. 111

114 (3) Flashing Point Temperature: Liquid fuel temperature at which the fuel starts combustion with small heat source close to the fuel. It is the temperature at which the vapor pressure of the liquid fuel is necessary and enough to burn. Though some kind of liquid fuel needs to be heated due to viscosity problem at low temperature in order to flow easily in pipe line, if the liquid fuel is heated to too high temperature relative to flashing point temperature, the fuel may easily be explosive. So the liquid fuel should be heated within appropriate range of temperature. Considering safety of combustion, preheating temperature should be 5~10 C, lower than flashing point temperature of the fuel. (4) Flame Temperature: In order to show fuel characteristics, Adiabatic Flame Temperature is specified. Adiabatic flame temperature is theoretical temperature of combustion product, which is obtained by complete combustion with theoretical amount of combustion air. Since it is not lowered by any loss, it is higher than actual flame temperature. In high temperature flame some part of CO 2 and H 2 O dissociate by thermal dissociation. Since thermal dissociation is heat absorption process, flame temperature with thermal dissociation becomes lower than flame temperature without thermal dissociation.flame temperature depends on pre-heating temperature and Oxygen concentration. (5) Specific Weight: Specific Weight is ratio of fuel density (g/cm 3 ) to water density (g/cm 3 ) at 4 C. Specific weight is determined by Chemical Composition of the Fuel. In the same category of fuel oil, the larger Specific Weight is, the larger C/H ratio is, and the more aromatic components are, the lower heating value is. (6) Kinematic Viscosity: In order to lessen transfer power loss and in order to obtain fine atomization at burner, liquid fuel needs to have low viscosity at burning time. For transportation kinematic viscosity needs to be 500~1000mm 2 /s, for atomizing at burner kinematic viscosity needs to be 20~45mm 2 /s. Figure shows Temperature dependence of kinematic viscosity of fuel oil. Figure Temperature vs. Kinematic Viscosity of Fuel oil *3 (7) Sulfur, Nitrogen, Ash: Sulfur and Nitrogen in fuel become not only the source of hazardous gas components against health, but also source of acid and corrosive gas components. When combustion gas becomes cool, ash sticks on the surface of heat exchanging tubes and causes choke of heat exchanger Burner & Combustion Air Ratio Control Though burner is a device to use thermal energy of fuel directly or indirectly to heat material by burning fuel, the burner has role not only to convert the chemical energy to thermal energy, but also to provide the thermal energy obtained by combustion to the material in the furnace, in accordance with material s characteristics and specific features. Burner can be classified by Fueland by Components. Though classifying the burner by Fuel, there are Gas burner, Oil burner and such Pulverized solid fuel burner as for coal and coke, there are no fundamental difference among such kinds of fuel. 112

115 Gas Burner Major burner components for industry are explained below: q Wind Box which stores and to uniformly supplies combustion air to burning part q Air Register which straightens air flow order to obtain the optimal mixture of fuel and combustion air to eject to combustion part. Air register is classified by structure into Radial Type, Axial Type and Baffle Type. q Ignition Burner or Pilot Burner with Igniting Electrode q Gas Nozzle, Oil Atomizer or Pulverized Coal ejecting Nozzle which ejects or atomizes fuel for easy burning. Oil Atomizer is classified into Hydraulic Type, High Pressure Air Flow Type, Low Pressure Air Flow Type, Rotary Type and Ultrasonic Sound Type. Hydraulic Type uses oil pump to pressurize fuel oil to eject from burner tip. High Pressure Air Flow Type uses pressurized air or steam with high pressure. Low Pressure Air Flow Type uses low pressure air flow. Rotary Type uses rotating disk which causes centrifugal force to make micro droplets of fuel oil. And Ultrasonic Sound Type uses ultrasonic transducer to make ultrasonic wave, which make surface wave over the oil surface. q Flame Stabilizer which makes combustion air swirl to accelerate contact with fuel and stabilize combustion q Burner Tile which is made of fire resistant brick to store heat for stabilization of Flame. Gas burner can easily mix fuel gas with air and it can make Oxidizing ambient or reducing ambient by adjusting mixing ratio. By mixing method of fuel gas and combustion air, gas burner is roughly classified into Diffusive Combustion Burner, Partial Pre-mixing Burner and Complete Premixing Burner. Diffusive Combustion Burner has no mixing chamber in the burner, but fuel and combustion air are individually ejected and mixed each other out of burner into the furnace. Since in Diffusive Combustion Burner no mixed gas of fuel and combustion air is fulfilled, no Back Fire is seen in the burner. So since in the Diffusive Combustion Burner, fuel and combustion Air can be safely heated without explosion, Diffusive Combustion Burner is widely used in the industry furnace. Partial Pre-mixing Burner and Complete Pre-mixing Burner have mixing chamber in the burner. Fuel and combustion air mix in the mixing chamber and after then mixture of fuel and combustion air ejects out of burner. Pre-mixing Burner can be used in higher heating load, and can make higher temperature flame. But flame of Pre-mixing Burner may be so unstable as back fire and extinguishing of flame are easily seen. In case of gas burning burner relative to oil burning burner, combustion flame has lower emissivity. In general gas burning flame has emissivity of 0.15~0.25, while oil burning flame has emissivity of about 0.5. In order to make higher emissivity of gas burning burner, two step combustion burner is applied. In the first step combustion is carried out with lack of air in order to dissociate Carbon grain in the flame, and in the second step all fuel including the dissociated Carbon grain is completely oxidized. In Partial Pre-Mixing Burner, primary combustion air and secondary combustion air is supplied. State of combustion is adjusted by changing ratio of primary/ secondary air. In Complete Pre-mixing Burner which has another name of Internal Mixing Burner, 100% of primary combustion air is preliminarily mixed with fuel in the mixing chamber without secondary 113

116 combustion air. It can heat with high speed heating, and it can be small in dimension. But since it is the most dangerous to easily have Back Fire in the burner, fuel supplying pipe or combustion air pipe. Figure shows Center Fire Type Burner is one example of gas burner, and Figure shows Ambient Pressure Burner as another example of gas burner. Figure Center fire burner *4 Figure shows Rotary Burner for Gas, Oil and Pulverized Coal. Air Swirl Vane and Gas Swirl Vane are located concentrically and with skewed angle those are effective to mix gas and air. Figure shows one sample of gas burner which burns BFG (Blast Furnace Gas) as the main fuel and Buthan as pilot fuel Oil Burner Figure shows two kinds of oil burners. Figure Ambient pressure gas burner *4 Figure Rotary Burner for Gas, Oil and Pulverized Coal *6 In oil burner there are two methods, one is Evaporating Combustion Method, and the other is Ejecting Combustion Method. In Evaporating Combustion Method, fuel oil is temporarily stored in oil pan or oil pot, in which oil is heated with steam or electric heater then the oil evaporates. The oil vapor flows down to burner to burn. Heavy oil is not suitable for Evaporating Combustion because residual Carbon is generated by thermal dissociation to choke burner nozzle. Such distillated oils as lamp oil (Kerosene) and Light Oil are suitable because residual Carbon is not generated by thermal dissociation from such kinds of oil. For Ejecting Combustion Method, all kinds of oil including heavy oil can be used. Oil is pressurized by pump to spray from burner nozzle. The finer oil mist grain is the more oil Figure Gas burner *2 Figure Oil burner *4 114

117 grain contact with combustion Air to burn. In order to obtain good combustion it is necessary to keep oil temperature for good oil viscosity, to keep oil pressure enough for spraying and to keep burner nozzle fine diameter. Figure shows Multi Lance Burner which can burn both of gas and oil as fuel Coal Combustion In Coal Combustion there are Grating Hearth Type Combustion and Pulverized Coal Type Combustion. In both of them coal ash which is generated by combustion may stick onto the surface of heat exchanger, draft control vane, flue wall and chimney wall. In Grating Hearth Type Combustion, lump coal with 5~25mm of grain size is supplied to burning grating hearth which is made of cast steel or cast iron. Through coal layer on the grating hearth, combustion air is blown. Coal is burnt with heat of burning coal and combustion air. Coal ash falls down thorough the burning grating to ash trough. In Pulverized Coal Type Combustion there are two kinds of supplying method. Both of them use coal as burnt material. The coal is crashed to Pulverized Coal with fine sized grain. One is Storage Tank Method, and the other is Direct Method. In Storage Tank Method coal is once stored in the storage tank, and then paid out in accordance with burning requirement to burner with combustion air. In Direct Method, material coal is crushed at pulverizing machine, and pulverized coal is directly transferred by air to burner. It is the most important to maintain burning face. Pulverized coal which is ejected out from burner, by receiving radiation heat or convection heat from combustion flame and furnace wall, ignited when temperature exceeds ignition point temperature. Ignition point temperature depends upon pulverized coal grain size and Oxygen concentration. Since generally the smaller grain size is, the shorter time it takes to ignite the pulverized coal, Burner for pulverized coal is to have high flowing speed at the exit of burner in order not to have back fire. Figure Multi Lance Burner *4 Figure Maximal Burner Capacity vs. Furnace hearth Area *2 Figure shows burner capacity appropriate to Furnace Hearth Area which is called Areal heating capacity (MJ/h/m2). It is significant to maintain good balance between burner capacity and furnace hearth area. If the burner capacity is too much for furnace hearth area, combustion gas cannot give combustion heat enough to the heated material. Figure shows Burner Tile which accumulates combustion heat in order to stabilize burner flame. Figure Burner tile *6 115

118 Figure Pusher Furnace with Five Zones *3 Figure Walking Beam Furnace with Six Zones * Material Transportation in the Furnace The oldest type of continuous re-heating furnace in Japan was Pusher Type Furnace, in which heated material is transported by pusher from charging gate to discharging gate. Though in accordance with increase of rolling capacity, heating capacity was increased as well as increasing of zones, material was still transferred by pusher. Pusher type furnace has advantage to be simple structure, but it sometimes causes surface defect on the product s bottom surface by abrasion with skid runner (or skid rail) on skid pipe. Pusher needs to transport material with pushing force which is equal to summed up resistance of the friction between material and skid runner. If skid pipe is too long or the friction force is too large, some part of the material may be piled up due to so called Buckling Figure shows an example of Pusher Type Five Zone Furnace again, and Figure shows an example of Walking Beam Type Furnace with six zones. In order to prevent such problems as surface defect due to abrasion with skid runner and buckling on the skid rail, instead of pusher type furnace, Walking Beam Type Furnace has been developed to transport the heated material in the re-heating furnace. The walking beam type furnace has two kinds of beam. One is Fixed Beam, and the other is Moving Beam. Moving beam moves both of vertically up/ down and horizontally forward/ backward. By using such both kinds of beams walking beam transports heated material longitudinally in the furnace. Though walking beam type furnace is better to prevent such problem as described above, generally it has another problem of cooling water heat loss, because it needs strong cooling against thermal deformation of the walking beam by weight of the heated material for a long heating time. After heating up, the bottom surface of the heated material becomes soft to be easily damaged by abrasion with skid rail or hearth. When the material is discharged, the material needs to be lifted not to slide on skid rail or hearth, in order not to have bottom surface damage. Such discharging device with lifting mechanism has been utilized in many countries not to have damage on the bottom surface of the material by abrasion Instrumentation (Measurement and Analysis) and Furnace Control In recent rolling mills, since various products have been manufactured from various kinds of material, heating condition is necessary to be adaptively adjusted in accordance with the conditions of materials and products. In order to solve such tasks, in re-heating furnace various measuring instruments and control systems are utilized. The purpose of such instruments and system is to improve: 116

119 q Control accuracy and control speed q Energy efficiency q Easy to operate q Maintainability q Effect to safety and environment In order to realize such requirements as above mentioned, the measuring instrument and control system need to have not only good accuracy, but also to be stable without unexpected break down trouble. Major control item are as follows, but details are omitted. q Furnace temperature control q Flow control (including flow ratio control) q Oxygen control in exhaust gas q Furnace pressure control q Safety control (combustion shut-down & recuperator protection) Especially in the Furnace Temperature Control, based upon material temperature at the charging point and predicted existing time in furnace, furnace temperature which is necessary to obtain optimal material discharging temperature, is calculated and heating load is adjusted in accordance with rolling specification, which includes steel grade, material dimension and product dimension. This control system eliminates personal deviation of furnace operation to obtain uniform discharging temperature which means to prevent over heat and under heat. It is useful for the least energy consumption, good product quality and safety. Figure shows a simple example of Furnace Control System. Figure Furnace Control System *3 In order to measure furnace temperature with fixed thermometer (pyrometer), thermocouple or temperature measuring resistance is used. When temperature of the moving material is measured, optical pyrometer may be used. The optical pyrometer can measure infrared radiation energy which is emitted from material surface, far from and without contacting the moving material. 117

120 There are such kind of thermocouples as R, K, N, E for Oxidizing ambient, and J and T for reducing ambient. Since the output signal level depends upon kind of thermocouple and measured temperature, thermocouple needs to be selected in accordance with measured temperature range and characteristics of ambient gas. Though especially R thermocouple is good for higher temperature than 1,000 o C, since it is very expensive it should be limited to use at only for high temperature. Flow rate of Gas and Water in closed pipe are measured with orifice plate or Pitot Tube with differential pressure transducer, Vortex type flow meter or float type flow meter. Flow rate of Oil is measured with such volumetric flow meter as oval gear type flow meter. When flow rate of air at the open channel or open end of closed tube, rotating vanes or Hot Wire type flow meter is used. Water flow rate in the closed pipe from out of the pipe is measured with ultrasonic or electromagnetic flow meter. When flow rate is measured, in order to obtain correct measurement, sometimes the measured value may be compensated with such circumferential parameters as temperature, pressure, viscosity, humidity and so on. It is necessary to take care that when differential pressure type flow meter, Vortex type flow meter, Ultrasonic type flow meter or Electromagnetic Flow meter is used to measure flow rate of the closed flow, since the measured value is strictly not Flow Rate but only Flowing Speed, in order to obtain measurement of Flow Rate, it is necessary to integrate the areal flowing speed in the flowing pipe or flowing channel with measured value by the measuring instruments.. Feed back Control, Feed forward Control and Adaptive Control When heating process including material condition and product condition are almost constant and stable, it is enough to apply Feedback Control Method, because the deviation of controlled result from aimed value is not large nor change in a short time. But if the heating process cannot be seen stable, it may be necessary to apply Feed Forward Control Method or Adaptive Control Method. In Feed back Control, control output is automatically made by control deviation between aimed value and controlled result, and the control output goes out to adjust such control device as valve actuator. In Feed forward Control, Control Output is made by using signal which comes from upper stream than controlled process. For example, material temperature at the entrance of charging point is fed forward to make control output. In Adaptive Control, Control Output is made by some signal coming from somewhere else which is relative to the objective process. The relation between processes is reflected to mathematical model equations, and the mathematical model is used to control. For example, when material thickness is known preliminarily, thickness information is fed to make compensating signal to usual feed back control. The adaptive controller makes mathematical equation of heat transfer phenomena regarding material thickness. If preliminarily operating order or operating logic is determined and stored, when such condition is realized, the process can be controlled by so called Sequence Control. Though the sequence Control was carried out by using relay device, in recent years semiconductor devices are used instead of relay to realize control logic. The most primitive control system in re-heating furnace is Combustion Control system, which is composed of Furnace Temperature Control and Flow Ratio Control between fuel and combustion air, furnace pressure control and combustion shut down control at the emergency time. Furnace Temperature Control and Flow ratio Control are usually cascaded, which means that output 118

121 signal of furnace temperature control system is fed to Flow ratio Control System. Roughly there are three methods in Combustion Control system. They are Fuel Preceding Serial Cascade, Air Preceding Serial Cascade and Parallel Cascade. Figure 10.25, Figure and Figure show combustion control system by Fuel Preceding Serial Cascade, Air Preceding Serial Cascade and Parallel Cascade each. In Fuel Preceding Serial Cascade, Fuel flow rate is firstly controlled by the output of furnace temperature control system, and Combustion Air flow rate is controlled by following the multiplied value of actual measurement of fuel flow rate by Theoretical amount of Combustion Air and Air Ratio (Air Excess Factor). In this system since Combustion Air flow rate always changes later than Fuel flow rate, when flow rate increases, air becomes less than required value for complete combustion, and when flow rate decrease, combustion air becomes excess than necessary amount for complete combustion. In Air Preceding Serial Cascade Combustion Air flow rate is firstly controlled by the output of furnace temperature control system, and Fuel flow rate is controlled by following the divided value of actual measurement of Fuel flow rate by Theoretical amount of Combustion Air and Air Ratio (Air Excess Factor). In this system since fuel flow rate always changes later than Combustion Air flow rate, when flow rate increases, fuel becomes less than required value for complete combustion, and when flow rate decrease, combustion air becomes less than necessary amount for complete combustion. In Parallel Cascade Combustion Air flow rate and Fuel flow rate are simultaneously controlled by the output of furnace temperature control system in parallel, In this system aimed value of Combustion Air flow rate is proportional to aimed value of Fuel flow rate, and it is multiplied by Theoretical amount of Combustion Air and Air Figure Serial Cascade Combustion Control System (Fuel proceeding) Figure Serial Cascade Combustion Control System (Air proceeding) Figure Parallel Cascade Combustion Control System Ration (Air Excess Factor). Since both of Fuel flow rate and Combustion Air flow rate change simultaneously, at whenever flow rate change, air ratio is kept constant. The result of Combustion is measured as Oxygen concentration in the exhaust gas with Oxygen meter. Especially in recent years, Oxygen meter based upon Zirconium sensor is widely used, which is directly inserted into furnace and it can easily measure Oxygen concentration in the exhaust gas. Computer Control Generally even if discharging temperature is same, when material dimension is different, heating load (or fuel flow rate) may be different in accordance with material dimension. In such a case due to difference of heating load, much heat loss takes place. 119

122 In order to obtain constant discharging temperature and little heat loss even with variety of material dimension, modern control system by utilizing computer has been applied in longer than 25 years. Figure shows an example of large scaled Furnace Control System. For such large scaled furnace control, computer is utilized to execute the followings control functions: (1) to make Charging Order of Heated Material into the furnace In accordance with Steel Grade, Material Dimension, Product Dimension, Scheduled Stop of Roll Exchanging, Charging Order is determined. It is the most significant for Energy Conservation in the furnace and rolling mill, Product Quality, Roll Availability. It is made without sudden fluctuation of material thickness and with gradual change of Product dimension. (2) to track and control material transportation Each material has such specified characteristics as steel grade, dimension, product dimension and so on. Computer needs to track the material movement around the furnace, including inside of the furnace. The computer controls material transportation in accordance with status of rolling operation, prediction of heating up, scheduled rolling mill stop and so on, in order to prevent over heat or under heat of the material, to minimize energy loss, to maximize productivity and to make product quality best. It is the most significant how to determine the discharging timing of heated material. It is determined by existing time in the furnace which is based upon state of heating, or by rolling pitch. If heating capacity of the furnace is larger than rolling capacity, the material is heated enough to specified heating temperature for rolling, and productivity of rolling becomes maximal. (3) to make up Set Value of Furnace Temperature (for each zone) In accordance with Steel Grade, Material Dimension, Product Dimension, Scheduled Stop of Rolling Operation and so on, Set Value of Furnace Temperature is determined. It is necessary to take care that it takes time for Heat Transfer, especially by conduction and convection, and that Temperature is time-integrated result of heat transfer phenomena. When non-scheduled operation stop happens, immediately operator estimates delay time due to the trouble, inputs the estimated delay time into the computer, and the set value is changed automatically in accordance with predicted operation delay in the computer. If necessary the computer may output not only decrease of furnace temperature set value, but also shut-down of combustion. (4) to make Set Value of Oxygen Concentration in exhaust gas Though usually Oxygen Concentration in exhaust gas is set at constant value, actually in the real furnace lower limit value of Oxygen Concentration in exhaust gas is affected by entrained air from out of furnace and characteristics of burner. Though when fuel flow rate is high, complete combustion can be realized and influence of entrained air is very little, when fuel flow rate is low, combustion may become incomplete and influence of entrained air can not be neglected. So set value of Oxygen Concentration in exhaust gas needs to be determined adaptively in accordance with fuel flow rate. (5) to carry out Control Action Furnace Control Computer (Controller exclusive for combustion control) executes narrow sense of control action. The control action means to make deviation between set value and fed back actual value which is measured by some measuring instruments, and to make control output in accordance 120

123 with some control logic which is contained in the computer, and to take out Output to the control actuator. (6) to log and analyze the controlled result In order to show relatives including operators, managers and executives, the stochastic data are logged and edited in the furnace control computer (Figure 10.28). Figure Furnace Control System Configuration *3 121

124 Flue & Draft Control (with Fan and Blower) Flue is prepared to exhaust combustion gas from furnace to chimney, and it is made of steel shell for supporting and shielding, and brick or ceramic fiber for thermal insulation. Chimney needs to have height enough to exhaust combustion gas from furnace thorough flue. So called Draft is pressure difference from entry of furnace to the top of chimney. When both of combustion fan and exhaust fan are installed, combustion air is supplied by the combustion fan into furnace, and after combustion, combustion gas is exhausted by exhaust fan. In such a case as supplied air by combustion fan is too little, or exhausted gas exhausted by exhaust fan is too much, furnace pressure becomes negative pressure, which means ambient air leaks into the furnace to cool down the furnace and heated material. And Oxygen in the leaked-in air makes scale on the surface of heated material. On the contrary, if supplied air by combustion fan is too much, or exhausted gas exhausted by exhaust fan is too little, furnace pressure becomes positive pressure, which means hot combustion gas leaks out from the furnace. And since leaked out combustion gas is very hot, such steel parts as furnace doors and furnace structure are burnt by the combustion gas. It introduces additional leak of combustion gas. In both cases heat loss takes place and thermal efficiency becomes low. Draft control system is composed of Furnace pressure sensor, controller and actuator. The furnace pressure sensor has narrow measuring range of about ±100Pa. Furnace pressure measuring port should be located at the height of material without affecting pressure fluctuation due to combustion flame. On the other hand at the entrance of reference pressure (ambient pressure) measuring port, hood would be better to put in order that external wind does not disturb the pressure measurement. The set value of draft control depends upon the height of pressure measuring point. If the measuring point is at the same height as material, the set value may be around +30~50Pa, which depends upon furnace specification in detail. Actuator for furnace control is damper at flue. The damper may be linear moving type or rotary type. Anyway the opening of damper is adjusted by control output signal in order that furnace pressure matches set value. Draft between entrance and exit of the furnace is composed of buoyancy and flowing resistance. The former is roughly proportional to multiplication of temperature and difference of height between furnace and the top of chimney. The latter is proportional to squared value of flow rate of combustion gas. If furnace temperature is almost constant, when fuel is supplied little, furnace pressure becomes low, and if fuel is supplied much, furnace pressure becomes high. Though if combustion gas can be exhausted enough even when fuel is supplied at most, no exhaust fan is necessary, otherwise exhaust fan is necessary to help exhausting combustion gas enough. It is necessary to take care that when extracting door opens, furnace pressure suddenly fluctuates. At that time if the furnace pressure control is in automatic mode, the control action is disturbed by opening of door. So at such a time automatic control should be shut and the control output should be held at value of just before the door opened, and cancelled to automatic mode just after door closed, in order to prevent disturbance due to opening the door. Figure shows Comparison of Electric Power Consumption of Fan by Flow Control Method. 122

125 Under condition that fan is rotated by full speed if flow rate is excess to required value, entrance damper or exit damper is choked in order to obtain aimed flow rate. In such cases fluid machine rotates in vain and electric power is consumed as friction heat in discharged fluid. It means that such full speed operation introduces energy loss, and speed needs to be controlled to required value. For the partial load operation such electrical methods as Primary Frequency Change and Pole Change or such mechanical method as Fluid joint are used. In addition regarding fan type, Axial type Fan has better partial load characteristics than Radial type Fan Refractory and Thermal Insulation Refractory is the general name of non-metallic Figure Comparison of Flow rate Control System *4 material which is hard to melt and it is used for heat resistant material in furnaces with very high temperature. It is roughly composed of Stereotype Refractory, Protean Refractory and Fiver type High Temperature Material. Stereotype Refractory includes variable bricks with same figure and same dimension which is made by casting in the mould. Protean Refractory includes Water hardening Cement with Fire Resistant Aggregate, Water hardening Plastic with Fire Resistant Aggregate, and Fiver type High Temperature Material includes so called Ceramic Fiber and so on. Refractory needs to have the following features: q to have resistant strength against the temperature and circumstantial condition q to have little volumetric change against the temperature fluctuation q to have no thermal crack against sudden temperature change q to have little degradation of structure against the temperature fluctuation q to have light heat mass which is defined by multiplication of weight and specific heat When furnace is constantly operated, thermal insulator, refractory, steel frame and furnace shell are heated to the constant temperature. In such a case, the outside of thermal insulator or furnace shell is steadily cooled down by radiation and convection heat transfer phenomena. If the furnace is intermittently operated, at the beginning stage of heating not only heated material in the furnace but also thermal insulator, refractory, steel frame and furnace shell are heated to the temperature of the balanced condition. It seems that the furnace structure including thermal insulator, refractory, steel frame and furnace shell stores heat during heating phase. When the furnace stops operation, even if fuel is not supplied to burner, the furnace structure is still hot and it dissipates accumulated heat for a long time. Such dissipated heat becomes loss. The stored and dissipated heat is proportional to heat mass of the thermal insulator, refractory, steel frame and furnace shell. 123

126 So the thermal insulator, refractory, steel frame and furnace shell need to have little heat mass. It means that such material as thermal insulator, refractory, steel frame and furnace shell need to have small density and small specific heat. For such purpose as thermal insulation for intermittently operated furnace, ceramic fiber is optimal material. Ceramic fiber is made of mainly alumina powder and fluorite powder, in addition, if necessary, B 2 O 3, ZrO 2, CrO 2 and TiO 2. The material powder mixture is heated to over 2000 C, melted and picked out as fine fiber. The fiber is picked out by the method of centrifugal force by rotating disc or ejecting from nozzle with high pressure. Chemically ceramic fiber is composed of about 50:50 of Alumina and Silica. But the maximum allowable temperature depends upon the mixing ratio of Alumina and Silica. In case of slightly more Silica than half, the maximum allowable temperature becomes 1260~ 1300 C, and in case of slightly more Alumina or in case of addition of Zirconia (ZrO 2 ) or other Oxides, the maximum allowable temperature becomes 1400~ 1500 C. Since ceramic fiber is rapidly changed from molten state to fiber, the fiber includes much Amorphous phase, when it is exposed to high temperature it changes to crystalline phase, and properties degrades. Relatively to Alumina contcnt the maximum allowable temperature of ceramic fiber is lower than brick with same concentration of Alumina, due to the crystalline phenomenon under high temperature. In order to prevent to degradation of ceramic fiber by crystalline phenomenon at high temperature, ceramic fiber with additional Alumina, and initially mixed crystallized fiber of Alumina into the amorphous fiber is sold. Though heat resistance is roughly determined by chemical content and crystallized material, such other fundamental properties as thermal conductivity strongly depends upon apparent bulk density. But in case of Shot is contained much into the fiber, which does not Figure Thermal Conductivity of Ceramic Fiber *3 become fine fiber but become spherical, it is necessary to take care that even if apparent bulk density is large due to existence of Shot, since the actual bulk density of fiber is not so large thermal conductivity is not so low. Ceramic fiber is processed into such various kinds of product as bulk, board, blanket, felt, and block. It is necessary to select which kind of ceramic fiber product in accordance with circumstance of use. Figure shows Temperature Dependence of Thermal Conductivity of Ceramic Fiber. 124

127 Table 10.6 Comparison of Insulated Heat & Accumulated Heat *4 (a) Shell Temperature and Radiating Heat through Flat Wall Wall Structure F ce Temp (1) 350mm Plastic Brick (2) +90mm Ceramic Fiber (3) 350mm Ceramic Fiber Shell Temp. C Rad. Heat kw/m 2 Shell Temp. C Rad. Heat kw/m 2 Shell Temp. C 1200 C C Rad. Heat kw/m 2 (b) Accumulated Heat in Furnace Wall Kind of Wall (1) Usual Brick (2) Insulating Refractory Brick 1st Layer [thickness (mm)/ Outer Temp ( C)] 2nd Layer [thickness (mm)/ Outer Temp ( C)] 3rd Layer [thickness (mm)/ Outer Temp ( C)] 4th Layer [thickness (mm)/ Outer Temp ( C)] 250mm Chamotte Brick/ 1107 C 125mm Insulating Refractory Brick/ 751 C 230mm Insulating Refractory Brick/ 782 C 40mm Insulating Board/ 517 C (3) Ceramic Fiber Blanket 50mm CF Blanket (for 1450 C )/ 1109 C 50mm CF Blanket (for 1260 C )/ 950 C 125mm Insulating Brick 40mm Rock Wool 100mm CF Blanket (for 1260 C )/ 550 C None None 50mm Rock Wool Unit weight (kg/m 2 ) Heat Loss (W/m 2 ) Accumulated Heat (MJ/m 2 ) 803 (100%) 217 (27%) 29 (3.6%) Note: Furnace Temperature 1250 o C, Ambient Temperature 90 C. In the CF Blanket, effect of stud is considered Table 10.6 shows Comparison of thermal insulation regarding engineering method. In comparison of heat dissipated from steel shell between thermally insulated by plastic refractory with Silica board and by ceramic fiber, the former is more than twice of the latter, with same inside temperature (1,200 o C) and same insulation thickness(130mm). In the other case, accumulated heat in three kinds of bricks with thickness of 500mm in total and in three kinds of ceramic fiber and one kind of rock wool blanket with thickness of 250mm in total are compared. In the latter case heat accumulated in the wall is only 3.6% of the former case, even though the temperature at both sides is almost same each other. In accordance with temperature increase, thermal conductivity of ceramic fiber also increases. It means that in accordance with temperature increase, resistance of heat transfer by conduction decreases. 125

128 10.12 Waste Heat Recovery In the reheating furnace there are roughly two types, one is combustion type and the other is electric type. Though the combustion type reheating furnace has an advantage that fuel cost is usually lower than electric power, it has such disadvantages as exhaust gas heat loss, hazardous comportment gas emission and contamination of material surface due to combustion gas. In order to decrease exhaust gas heat loss, there are two kinds of solution countermeasure, one is installation of heat exchanger so called Recuperator, and the other is expansion of furnace length. recuperator is a heat exchanger of which heat source is combustion gas after heating the heated material, and heat sink is combustion air or fuel which is supplied to burner. Installation of recuperator has an advantage that furnace main body is independent of installation of the recuperator, but the recuperator can be installed separately from furnace main body on the flue Disadvantages of the recuperator are maintenance cost of the recuperator which is caused mainly by ash and acid. The former sticks on the surface of heat exchanging tubes and let the heat exchanger choke, and the later causes corrosion of heat exchanging tubes due to acid condensation after cooled down. It causes blocking of combustion gas, and leak of air or combustion gas. In addition when the recuperator is added to current furnace, combustion air or fuel gas expands by heating, it increases flowing resistance in the pipe. The type of recuperator is classified with heat transfer principle and flowing direction of fluid. Regarding heat transfer principle, one is radiation type for high temperature combustion gas, and the other is convection type for middle temperature combustion gas. Regarding flowing direction, there are Counter flow type, Parallel flow type and Cross flow type. In the Counter flow type recuperator with infinity heat transfer surface area, the combustion air temperature at the exit of the recuperator can reach entry temperature of the exhaust gas. In the parallel flow type recuperator, even though with infinity heat transfer surface area, the combustion air temperature at the exit of the recuperator cannot reach exit temperature of the exhaust gas. The other classification of recuperator is by material. There are recuperators made of steel pipes, steel plates, cast steel, ceramics or refractory. Ten years or more ago accumulative heat exchanging burner, so called Regenerative Burner has been used. The regenerative burner is composed of usual burner, heat accumulation blocks and switching valves. Though preheated air temperature at the Regenerative burner may reach over 1000 o C, since heat accumulation block and switching valves may be easily broken by the repetitive thermal shock due to rapid temperature fluctuation between hot combustion gas and cold combustion air. If the switching valves are broken or deformed by thermal shock or thermal expansion, combustion gas or combustion air leaks to drop thermal efficiency. When pulverized coal is used for fuel, since preheated hot air cannot be used for coal transportation because of danger of explosion, use of recuperator is not practical. In addition coal ash generated by combustion sticks on the surface of heat exchanging tubes, which causes choke and corrosion of heat exchanging tubes. When furnace length is expanded, combustion gas heats the material in the furnace enough so as 126

129 to combustion gas temperature drops enough. In such a case even though without recuperator, combustion air is heated, thermal efficiency becomes high. It is necessary to take care that if the heated material is transported in the furnace by pusher, too long furnace length may cause piled-up of pushed material on the skid pipe. The piled-up material makes transportation difficult, and in addition it causes choking of combustion gas flow thorough the furnace. The critical condition whether the material is piled-up or not depends upon the friction coefficient of material and skid slider as well as shape of the material Explosion and Environmental Problems In the furnace with fuel combustion if the fuel is burnt with normal burning speed, the furnace can be operated safely. But if the fuel burns too fast, explosion may take place. In order to generate combustion, fuel which is burnt, the heat which is energy source to start combustion and Oxygen which supports combustion. The ratio between fuel and Oxygen needs to be within certain range which is called Explosion limit. The energy to start combustion is shown as Ignition Temperature in accordance with kind of fuel. Even if one parameter is within dangerous range, if other parameter is out of dangerous range, explosion can be prevented. Though usually such solid fuel as coal is less explosive than gaseous or liquid fuel, pulverized coal especially in case of pulverized coal with very fine grain coal is easy to explode, similarly to combustible gas. In order to use Re-heating Furnace under safe condition, it is necessary to design and to install facilities and system for Fail Safe and Fail Proof to prevent Explosion and Air Pollution by abnormal operation. Fail Safe and Fail Proof are based upon concept that any plant may be broken, and any operator may have miss-operation, and even if some part of facilities is broken, or some operator perpetrates miss-operation, if the furnace including control system is made under the concept of Fail Safe and Fail Proof, the furnace will not have so serious explosion. Table 10.7 shows major causes of explosion at furnace. About 60% of explosion is caused by personal miss operation, and about 60% of explosion is took place at the starting stage of combustion. They mean that most of explosion takes place in the unsteady stage of combustion, especially in the ignition stage. 127

130 Table 10.7 Major Causes and Timing of Explosion at Re-heating Furnace Cause Start Combustion End Total Operation 15 (30.6%) 10 (20.4%) 3 (6.1%) 28 (57.1%) Facilities 13 (26.6%) 6 (12.2%) 2 (4.1%) 21 (42.9%) Total 28 (57.2%) 16 (32.6%) 5 (10.2%) 49 (100%) In order to prevent such explosion problem, such notes as the Table 10.8, including consistent training of correct operating procedures and appropriate facilities maintenance activities are necessary. Table 10.8 Major Countermeasures to prevent Furnace Explosion No. Countermeasures 1 To aware and to understand on the Safety at the Furnace 1-1 To understand the Characteristics of Fuel and safe using manner of the Fuel 1-2 To prevent Leakage of the Fuel. If the fuel leaks out, immediately stop to use the fuel and ventilate the leaked fuel in the room. 1-3 To select and use Burner appropriate for stable combustion 1-4 To install the Emergency Shut-Down System and immediately shut down when combustion becomes abnormal. 1-5 To purge the remaining combustible gas around burner prior to ignition with specified amount of purging gas 1-6 To ignite Burner following to right operating procedures and at correct igniting position. And to assure that combustion has started. 1-7 When combustion is abnormally shut-down, after making sure the cause of the shut-down, remove the cause and purge the remaining combustible gas. 1-8 To ignite, burn and extinguish the Burner following correct operating procedures. 1-9 To maintain the Furnace Facilities at right condition with daily and periodical Maintenance Activities. 2 To make Furnace Facilities safe, with safe system following to safe criteria. 3 To execute right operation and maintenance activities, to make sure the correct state of the furnace, to maintain the facilities periodically and to use the furnace facilities correctly Facilities Maintenance for Stable Operation and Excellent Product Quality In order to manufacture product with excellent quality under stable condition in accordance with required sales order, it is fundamentally necessary to maintain the facilities relative to reheating furnace to rolling mill. When rolling machines and around rolling machine has some trouble not to operate, the reheating furnace cannot continue to discharge the material in the furnace. It causes over heat of the material to make scale on the material surface. In some cases the material surface is oxidized not only to generate scale but also to be molten down. Such over heating causes serious problem on both of thermal efficiency, product quality and material yield. 128

131 When the material in the furnace is transported by walking beam, since the material in the furnace can have gap in the longitudinal direction among materials, even if such former facilities of the furnace as pusher, material transporting table has some trouble, the material in the furnace can be transported independent of former facilities. But in case of facilities in the upper stream of the furnace have some trouble the material in the furnace can be transported in longitudinal direction in the furnace with walking beam independently of the material at the upper stream facilities. In the pusher type furnace, since the material in the furnace cannot have gap in the longitudinal direction among material, when upper stream facilities of the furnace have some troubles, the material in the furnace cannot be transported, because the material in the upper stream can neither be supplied into the furnace nor push the material in the furnace. The other major maintenance objective is burner. If burner is not maintained enough, combustion does not become complete. It causes serious problem of low thermal efficiency and serious effect on air pollution due to black smoke and explosion. In order to have complete combustion and stable operation throughout furnace and rolling mill, maintenance activities based upon operating condition and based upon prescheduled maintenance plan need to be executed Future Re-heating Furnace for Steel Rolling Energy conservation should be carried out covering over all energy sources not only fuel but electric power, water, compressed air, steam etc. Especially saving of thermal energy is closely related to environmental affairs, and it is very significant. In order to realize energy conservation, it is necessary for furnace manufacturer to design the furnace which minimizes energy consumption, and for furnace user to operate the furnace in order that the furnace can be finely operated with such controlling technologies with computer as material charging order determination and over-heating prevention when rolling operation unexpectedly stops. In order to decrease heat loss of combustion type Steal Material Re-heating Furnace, such countermeasures are useful as Table Though various new reheating furnaces for steel rolling have been already developed, they have some limitations due to fundamental back ground. For example Low NOx Burner, Heat Accumulating Burner (Regenerative Burner), Air Ratio Control based upon Oxygen concentration analysis in the waste gas and Rotating Speed Control of fan for variable flow rate and so on. When such newly developed furnace or new combustion technologies are applied to the furnace improvement plan at Rolling Mills Cluster in Bhavnagar Area, such constraint conditions as material, fuel, installation space, disturbance to operation by unexpected facilities trouble need to be released or removed. Such new technologies need to be discussed and considered among rolling mills, academic parties and engineering parties. 129

132 Figure Thin Slab Caster & Strip Rolling Mill *3 In recent years in some countries Direct Iron ore Reducing Furnaces are installed. The molten iron metal is refined by some refining furnace to steel. After then continuous thin slab casting machines are installed after the refining furnace, and thin slab which is cast in the continuous caster is inserted to recovering furnace to recover the surface temperature by own internal heat enough to roll. The thin slab is slightly rolled by rolling mill to product. Though it is energy efficient process, in order to smoothly operate the process, it is necessary to maintain whole facilities in high availability with excellent maintenance activities, and it is necessary to continue the operation without unexpected trouble. Figure shows the new process with Continuous Thin Slab Caster Table 10.9 Countermeasures for Energy Conservation of Re-heating Furnace Rough Countermeasure 1. Visible heat loss reduction of material 2. Waste gas loss reduction 3. Dissipation heat reduction 4. Improvement of combustion Detail Countermeasure Material charging temperature up by hot charging Material discharging temperature down Waste gas temperature down by furnace length expansion or good heat transfer Heat pattern with inter-zone separation Areal cover ratio in furnace Volumetric heating capacity in furnace Recuperator or boiler to recover waste gas heat Improvement of thermal insulator Appropriate dimension of furnace body Seal of opening ports around furnace Seal at charging and discharging door Shortening door opening time duration Thermal insulation of hot air pipe Route and dimension of hot air pipe Thermal insulation of water cooled skid Lay out and number of water cooled skid High entry temperature of cooling water Fuel with high heating value Burner with appropriate flame length Combustion with low air ratio High accuracy air ratio control Reduction of entrain air by draft control 130

133 10.16 Reference List Name of Book Publisher Editor Year Eutectic in free encyclopedia Wikipedia ja.wikipedia.org/ 10 Iron & Steel Handbook The 3id Edition, III (1) Base of Rolling, Plate & Strip Maruzen ISIJ 80 New Edition Industrial Furnace Handbook Textbook for The 4th Special Lecture on Thermal Field Handbook on Energy Conservation Audit Technologies (for Factory) The 5th Edition Lecture on Heat Management Technologies ECCJ Japan Industrial Furnace 97 Association ECCJ ECCJ 07 ECCJ ECCJ 07 Maruzen Central Heat Management Association (Japan) 72 [Note] ISIJ: The Iron and Steel Institute of Japan; ECCJ: Energy Conservation Center, Japan 131

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136 For more details, please contact: Debajit Das, Program Manager, Climate Change/Environment Winrock International India 788, Udyog Vihar, Phase V, Gurgaon , Haryana, Tel: ; Fax: debajit@winrockindia.org; Web: Registered Office: S-212, 2 nd Floor, Panchsheel Park, New Delhi Tel: ; Fax: Designed by: Outreach Division, WII